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AP Calc AB · Mathematics
Integrals · Antiderivatives

Antiderivatives of Rational Functions and Integration by Parts

Before you start, make sure you know: Polynomial factorization (Algebra 2)
Before you start, make sure you know: Operations with algebraic fractions (Algebra 2)

A streaming app logs how fast data arrives at its server: $v(t) = \dfrac{4}{t+1}$ GB per minute, where $t$ is in minutes. You know the rate. How much data is stored after $t$ minutes? To undo a derivative you need an antiderivative, and $\dfrac{4}{t+1}$ is a quotient of polynomials, a rational function. This page gives you the toolkit for those, plus integration by parts for products like $x e^x$.

Antiderivatives and the basic table

Each antiderivative in the family is the same curve slid up or down. Drag the slider and watch the graph shift.

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Find the primitive of the following polynomial function using the basic rules of integration: $f(x) = 6x^5 - 4x^3 + 3x^2 - 2$

Find the primitive of the following polynomial function using the basic rules of integration:

$f(x) = 6x^5 - 4x^3 + 3x^2 - 2$

Solve
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Determine the function $F(x)$ which is a primitive of $f(x) = e^x + 2x$ and satisfies the condition of passing through the point $P(0, 5)$.

Determine the function $F(x)$ which is a primitive of $f(x) = e^x + 2x$ and satisfies the condition of passing through the point $P(0, 5)$.

x y 5 1 O P(0, 5) + C = ? F(x) = ? Family of primitives f(x) = ex + 2x F(x) = ∫f(x)dx P(0, 5) ∈ F(x)
Solve
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Find the integral of the function $f(x)$ which combines powers and roots, by first expressing the roots as fractional indices: $f(x) = \sqrt{x} + \frac{1}{x^2}$

Find the integral of the function $f(x)$ which combines powers and roots, by first expressing the roots as fractional indices:

$f(x) = \sqrt{x} + \frac{1}{x^2}$

Solve

Logarithm form: numerator = derivative of the denominator

Matching the numerator 6x + 3 with three times the derivative of the denominator x squared plus x plus 7, so the integral is 3 ln of the denominator. (x² + x + 7)′ = 2x + 1 6x + 3 = 3 · (2x + 1) ∫ (6x + 3)/(x² + x + 7) dx = 3 ln(x² + x + 7) + C
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Find the set of all primitive functions of the following rational function, using the linearity properties of the integral: $$f(x) = \frac{7}{x - 5}$$

Find the set of all primitive functions of the following rational function, using the linearity properties of the integral:

$$f(x) = \frac{7}{x - 5}$$
Solve
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Calculate the following logarithmic indefinite integrals, adjusting the constants if necessary: a) $\displaystyle \int \frac{5}{x+3} dx$ b)…

Calculate the following logarithmic indefinite integrals, adjusting the constants if necessary:

  1. a) $\displaystyle \int \frac{5}{x+3} dx$
  1. b) $\displaystyle \int \frac{2x}{x^2 - 1} dx$
Solve
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Calculate the following indefinite integral by observing that the numerator is, or can be easily transformed into, the derivative of the denominator: $$\int \frac{2x +…

Calculate the following indefinite integral by observing that the numerator is, or can be easily transformed into, the derivative of the denominator:

$$\int \frac{2x + 3}{x^2 + 3x + 10} \, dx$$
Solve

If the numerator's degree is not smaller: divide first

Polynomial division splits P(x) over Q(x) into a polynomial quotient C(x), integrated with the power rule, plus a proper fraction R(x) over Q(x). P(x) Q(x) = C(x) + R(x) Q(x) polynomial:power rule proper fraction:deg R < deg Q
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Divide the numerator polynomial by the denominator (or decompose the fraction into several terms) to solve the following integral: $$\int \frac{x^3 - 4x^2 + 5}{x^2} \,…

Divide the numerator polynomial by the denominator (or decompose the fraction into several terms) to solve the following integral:

$$\int \frac{x^3 - 4x^2 + 5}{x^2} \, dx$$
Solve
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Calculate the primitive of the function $g(x)$ by making a prior adjustment in the numerator to obtain an integer part and a fractional part: $$g(x) = \frac{x + 5}{x +…

Calculate the primitive of the function $g(x)$ by making a prior adjustment in the numerator to obtain an integer part and a fractional part:

$$g(x) = \frac{x + 5}{x + 1}$$ ? x = −1 y = 1 x y 0 (0, 5) (−5, 0) g(x) = (x+5)/(x+1) g(x) = ? + ?/(x+1) ∫ g(x) dx = ?
Solve
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A market study analyzes the growth rate of sales for a new model of electric scooter. The function describing the rate of change of sales (in hundreds of units per…

A market study analyzes the growth rate of sales for a new model of electric scooter. The function describing the rate of change of sales (in hundreds of units per month) is given by:

$f(x) = \dfrac{x^2 + 2x + 3}{x + 1}$

where $x$ is the time in months. Calculate the family of total sales functions $F(x)$ by obtaining the antiderivative of this function. (Note: Perform polynomial division first).

1 3 5 7 3 6 y = x + 1 Time x (months) Rate f(x) f(x) F(x) = ∫f(x)dx Total Sales
Solve

Distinct real roots: one fraction per factor

To find the constants, factor $Q$ (quadratic formula, factoring, or synthetic division for higher degrees; some problems call synthetic division Ruffini's rule). Multiply both sides by $Q$, then plug in each root.

Here a rational function (green) is the sum of its two pieces. Compare the graphs.

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Decompose the integrand into partial fractions to calculate the integral of this rational function with distinct real roots in the denominator: $$\int \frac{1}{x^2 - 9}…

Decompose the integrand into partial fractions to calculate the integral of this rational function with distinct real roots in the denominator:

$$\int \frac{1}{x^2 - 9} \, dx$$
Solve
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Determine the integral of the following rational function by previously decomposing it into a sum of simpler fractions:…

Determine the integral of the following rational function by previously decomposing it into a sum of simpler fractions:

$\displaystyle \int \dfrac{x + 7}{x^2 + 4x + 3} \, dx$

x + 7 x² + 4x + 3 = x + 7 (x + 1) (x + 3) = A x + 1 + B x + 3
Solve
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Calculate the indefinite integral of the following rational function with three distinct real roots in the denominator:…

Calculate the indefinite integral of the following rational function with three distinct real roots in the denominator:

$\displaystyle \int \dfrac{2x^2 - x}{(x-1)(x+1)(x+2)} \, dx$

−3 −2 −1 0 1 2 3 1 −1 f(x) = 2x² - x (x-1)(x+1)(x+2) Decomposition: ∫ ( ? x-1 + ? x+1 + ? x+2 ) dx
Solve

Repeated roots: one fraction per power

A double root factor (x minus a) squared produces two partial fractions: A1 over (x minus a), which integrates to a logarithm, and A2 over (x minus a) squared, which integrates to a power. (x − a)² double root A₁/(x−a) A₂/(x−a)² A₁ ln |x−a| −A₂/(x−a) integrates to
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Calculate the indefinite integral of the following rational function by decomposing it into partial fractions, knowing that its denominator has a repeated real root:…

Calculate the indefinite integral of the following rational function by decomposing it into partial fractions, knowing that its denominator has a repeated real root:

$\displaystyle \int \dfrac{5x - 2}{x^2 - 4x + 4} \, dx$

Solve
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Determine the values of the parameters $A$, $B$ and $C$ so that the following equality is true and, subsequently, calculate the antiderivative of $f(x)$ that vanishes at…

Determine the values of the parameters $A$, $B$ and $C$ so that the following equality is true and, subsequently, calculate the antiderivative of $f(x)$ that vanishes at $x=0$:

$$\int \frac{x^2 + 5x + 2}{(x+1)^2(x-2)} \, dx = \int \left( \frac{A}{x+1} + \frac{B}{(x+1)^2} + \frac{C}{x-2} \right) \, dx$$ x = −1 x = 2 1 2 −1 1 −1 x y f(x) f(0)=−1 f(x) = A/(x+1) + B/(x+1)² + C/(x-2) A = ? , B = ? , C = ? ∫ f(x)dx = F(x) , F(0) = 0
Solve
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Calculate the antiderivative of the function $f(x) = \dfrac{x^4 + x^3 - 2}{x^3 - x^2}$ that passes through the point $P(2, 5)$. Note that, due to the degrees of the…

Calculate the antiderivative of the function $f(x) = \dfrac{x^4 + x^3 - 2}{x^3 - x^2}$ that passes through the point $P(2, 5)$. Note that, due to the degrees of the polynomials, you will need to perform polynomial division first and then decompose the remaining fraction considering the existence of repeated real roots.

x y F(x) + C₁ F(x) + C₂ F(x) P(2, 5) 2 5
Solve

Quadratics with no real roots: arctangent

A quadratic like $x^2 + 9$ or $x^2 - 4x + 13$ has a negative discriminant ($b^2 - 4ac < 0$), so it cannot be factored over the reals. Its antiderivative is an arctangent.

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Determine the indefinite integral of the following function, whose form corresponds to an arctangent-type primitive: $$\int \frac{3}{x^2 + 16} \, dx$$

Determine the indefinite integral of the following function, whose form corresponds to an arctangent-type primitive:

$$\int \frac{3}{x^2 + 16} \, dx$$
Solve
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In arctangent-type integrals, it is sometimes necessary to manipulate the denominator. Calculate the following primitive by completing the square in the denominator so…

In arctangent-type integrals, it is sometimes necessary to manipulate the denominator. Calculate the following primitive by completing the square in the denominator so that it takes the form of type $\int \frac{u'}{1+u^2} dx$:

$\displaystyle \int \dfrac{3}{x^2 + 2x + 5} \, dx$

Solve

A logarithm and an arctangent together

When the denominator is an irreducible quadratic and the numerator is $Mx + N$, split the numerator into a piece that matches the derivative of the denominator (a log) plus a constant leftover (an arctangent).

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Find the family of functions $F(x)$ resulting from integrating the function: $f(x) = \dfrac{2x + 5}{x^2 + 9}$ Hint: Separate the integral into two parts, one resulting…

Find the family of functions $F(x)$ resulting from integrating the function:

$f(x) = \dfrac{2x + 5}{x^2 + 9}$

Hint: Separate the integral into two parts, one resulting in a natural logarithm and another in an arctangent function.

Solve
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A team of engineers is monitoring the coolant flow in a thermal power station. The rate of change of the liquid volume with respect to time $t$ is given by the function…

A team of engineers is monitoring the coolant flow in a thermal power station. The rate of change of the liquid volume with respect to time $t$ is given by the function $v(t) = \dfrac{4t + 10}{t^2 + 4t + 13}$. Find the expression for the total volume $V(t)$ given that at the initial time ($t=0$) the tank contained $100$ gallons.

Note: Observe that the denominator has no real roots, so the solution will combine a natural logarithm and an arctangent.

COOLANT TANK t = 0 V(0) = 100 gal t > 0 V(t) = ? v(t) = 4t + 10 t² + 4t + 13
Solve

Partial fractions with an irreducible factor

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Calculate the indefinite integral $\displaystyle \int \frac{3x^2 + 1}{x^3 + x^2 + x + 1} \, dx$. To do this, observe that the denominator can be factored using Ruffini's…

Calculate the indefinite integral $\displaystyle \int \frac{3x^2 + 1}{x^3 + x^2 + x + 1} \, dx$.

To do this, observe that the denominator can be factored using Ruffini's rule or by grouping terms, resulting in a product of a linear factor and an irreducible quadratic factor.

Solve
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Determine the indefinite integral of the function $g(x) = \dfrac{1}{x^4 - 1}$. To solve this exercise, you must factor completely over the real numbers and decompose the…

Determine the indefinite integral of the function $g(x) = \dfrac{1}{x^4 - 1}$. To solve this exercise, you must factor completely over the real numbers and decompose the fraction into a sum that includes terms with distinct real roots and a term with complex roots of the arctangent type.

Solve

Substitution that turns a function into a rational one

Not every integrand looks rational at first. If $e^x$ or $\sqrt{x}$ appears, a substitution can turn it into a rational function of a new variable. Then you use everything above.

Plan for integrals containing e to the x: substitute u equals e to the x, integrate the rational function of u with partial fractions, then substitute back. u = eˣ, du = eˣ dx rational function of u partial fractions in u back-substitute u = eˣ
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Find the set of all antiderivatives of the following function, first making a suitable substitution that transforms it into a rational function: $$f(x) = \frac{e^{2x} +…

Find the set of all antiderivatives of the following function, first making a suitable substitution that transforms it into a rational function:

$$f(x) = \frac{e^{2x} + e^x}{e^{2x} - 4}$$
Solve
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Calculate the antiderivative of the function $h(x) = \dfrac{x^5 + x^2}{x^3 - 1}$. Before integrating, simplify the expression by polynomial division and check if there…

Calculate the antiderivative of the function $h(x) = \dfrac{x^5 + x^2}{x^3 - 1}$. Before integrating, simplify the expression by polynomial division and check if there is any standard identity or factorization that allows you to reduce the complexity of the integrand before applying partial fraction decomposition.

Solve

Integration by parts

Products such as $x e^x$ or $x\cos x$ do not fit any rule so far. Reverse the product rule.

A rectangle of area u times v split by a curve into two regions whose areas are the integral of v du and the integral of u dv. ∫ v du ∫ u dv u v ∫ u dv + ∫ v du = uv

Pick $u$ so that $du$ is simpler than $u$, and $dv$ so that you can integrate it. The mnemonic LIATE ranks what to choose as $u$: Logarithmic, Inverse trig, Algebraic (polynomials), Trigonometric, Exponential. The first type in the list that appears in the integrand is $u$.

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Use the method of integration by parts to solve the following integral. Remember to choose $u$ and $dv$ appropriately following the LIATE mnemonic:…

Use the method of integration by parts to solve the following integral. Remember to choose $u$ and $dv$ appropriately following the LIATE mnemonic:

$\displaystyle \int x \cdot e^x dx$

Solve
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Solve the following integral using the method of integration by parts: $\displaystyle \int (x + 2) \cdot \cos(x) dx$

Solve the following integral using the method of integration by parts:

$\displaystyle \int (x + 2) \cdot \cos(x) dx$

∫ (x + 2) · cos(x) dx u = x + 2 Differentiate du = dx dv = cos(x) dx Integrate v = sin(x) ∫ u dv = u · v - ∫ v du
Solve
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Calculate the primitive of the function $f(x) = (2x + 3) \cdot e^x$ whose graph intersects the y-axis ($OY$-axis) at the point $(0, 5)$. Use the method of integration by…

Calculate the primitive of the function $f(x) = (2x + 3) \cdot e^x$ whose graph intersects the y-axis ($OY$-axis) at the point $(0, 5)$. Use the method of integration by parts and check the result by differentiating the obtained function.

Solve

Applying parts more than once

When the polynomial has degree $2$ or more, each round lowers its degree by one. Keep the same choice of $u$ (the polynomial) each time.

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Find the primitive of the function $g(x) = x^2 \cdot \cos(x)$ that passes through the origin. You will need to apply the method of integration by parts twice…

Find the primitive of the function $g(x) = x^2 \cdot \cos(x)$ that passes through the origin. You will need to apply the method of integration by parts twice consecutively.

Solve
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Calculate the primitive of the function $g(x) = x^2 \cdot \ln^2(x)$ given that its graph passes through the point $P(1, \frac{2}{27})$. To do this, you will need to…

Calculate the primitive of the function $g(x) = x^2 \cdot \ln^2(x)$ given that its graph passes through the point $P(1, \frac{2}{27})$. To do this, you will need to apply the method of integration by parts successively.

Solve

Cyclic integrals: the original comes back

For $e^{ax}\sin(bx)$ or $e^{ax}\cos(bx)$, neither factor ever gets simpler. But after two rounds the original integral reappears, and you solve for it like an equation.

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Find the indefinite integral $\int e^{2x} \cdot \sin(x) \, dx$. These types of integrals are called "cyclic". Apply the method of integration by parts until the original…

Find the indefinite integral $\int e^{2x} \cdot \sin(x) \, dx$.

These types of integrals are called "cyclic". Apply the method of integration by parts until the original integral appears again and solve for its value.

Solve
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In the study of alternating current electrical circuits, the current intensity $i(t)$ in amperes is usually modeled by functions combining exponentials and…

In the study of alternating current electrical circuits, the current intensity $i(t)$ in amperes is usually modeled by functions combining exponentials and trigonometrics. Suppose that the rate of change of the charge of a capacitor is given by the function:

$$f(t) = e^{-2t} \cdot \cos(3t)$$

Calculate the set of all primitive functions $F(t)$ associated with this intensity using the method of integration by parts. Note that these types of integrals are solved by the "iteration" or "cyclic" method.

? e⁻²ᵗ -e⁻²ᵗ t f(t) 1 2 3 1 −1 f(t) = e⁻²ᵗ·cos(3t) F(t) = ∫ f(t) dt = ? Method: By parts (Cyclic)
Solve
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Determine a function $f(x)$ whose derivative is $f'(x) = \cos(\ln x)$. Help: Use the method of integration by parts considering $u = \cos(\ln x)$ and $dv = dx$. After…

Determine a function $f(x)$ whose derivative is $f'(x) = \cos(\ln x)$.

Help: Use the method of integration by parts considering $u = \cos(\ln x)$ and $dv = dx$. After applying it twice, you will obtain an expression where the original integral appears, allowing you to solve for it.

Solve

Logarithms and inverse trig functions alone

How do you integrate $\ln x$ or $\arctan x$ when there is no second factor? Make one: $dv = dx$. Take $u = \ln x$ (or the inverse trig function), and the new integral comes out algebraic.

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Calculate the primitive of the natural logarithm function using the method of integration by parts, taking $u = \ln(x)$ and $dv = dx$: $\displaystyle \int \ln(x) dx$

Calculate the primitive of the natural logarithm function using the method of integration by parts, taking $u = \ln(x)$ and $dv = dx$:

$\displaystyle \int \ln(x) dx$

Solve
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An electronic components company estimates that its marginal cost (the cost of producing one additional unit) follows the function $C'(x) = x \cdot \ln(x)$, where $x$ is…

An electronic components company estimates that its marginal cost (the cost of producing one additional unit) follows the function $C'(x) = x \cdot \ln(x)$, where $x$ is the number of thousands of units produced.

Determine the total cost function $C(x)$ given that the fixed costs (cost when $x = 1$, in this simplified model) are $10$ thousand dollars.

units (thousands) C'(x) C'(x) = x·ln(x) ∫ x·ln(x) dx 0 1 C(1)=10 x
Solve
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Calculate the indefinite integral of the function $h(x) = \text{arctg}(2x)$. Hint: Use the method of integration by parts taking $u = \text{arctg}(2x)$ and $dv = dx$.…

Calculate the indefinite integral of the function $h(x) = \text{arctg}(2x)$.

Hint: Use the method of integration by parts taking $u = \text{arctg}(2x)$ and $dv = dx$. Remember that the derivative of $\text{arctg}(f(x))$ is $\frac{f'(x)}{1 + [f(x)]^2}$.

Solve

Combining techniques

Some integrals need a substitution first and parts second, or parts with a cleverly chosen $dv$.

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Calculate the primitive of the function $h(x) = \operatorname{arc sen}(\sqrt{x})$. Hint: First make a substitution of the type $x = t^2$ to eliminate the root and,…

Calculate the primitive of the function $h(x) = \operatorname{arc sen}(\sqrt{x})$.

Hint: First make a substitution of the type $x = t^2$ to eliminate the root and, subsequently, apply the method of integration by parts.

x y 0 1 π/2 y = arcsin(√x) x = sin²(y)
Solve
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There are integrals that require great technical skill to decompose the integrand before applying the method of parts. Calculate the following indefinite integral using…

There are integrals that require great technical skill to decompose the integrand before applying the method of parts. Calculate the following indefinite integral using the strategic substitution $u = x \cdot e^x$ at some point in the process or by operating directly by parts:

$$\int \frac{x \cdot e^x}{(x+1)^2} dx$$
Solve

Pinning down the constant

An antiderivative family is a stack of identical curves. One piece of extra information selects the curve you need.

Three parabolas y equals x squared over 2 plus C for C equal to minus 1, 0 and 1; only the one with C equal to 1 passes through the point P(2, 3). C = −1 C = 0 C = 1 P(2, 3)
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Find the function $f(x)$ given that its derivative is $f'(x) = \frac{1}{x + 2}$ and that its graph passes through the point $P(0, 5)$.

Find the function $f(x)$ given that its derivative is $f'(x) = \frac{1}{x + 2}$ and that its graph passes through the point $P(0, 5)$.

Solve
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A team of engineers is analyzing the discharge rate of the battery of a new drone prototype. They have determined that the function representing the rate of change of…

A team of engineers is analyzing the discharge rate of the battery of a new drone prototype. They have determined that the function representing the rate of change of the charge (in mAh per minute) is given by $f(t) = 3t^2 - \frac{4}{t+1} + \sqrt{t}$, where $t$ is the time in minutes.

Find the total charge function $F(t)$, given that at the initial time ($t = 0$) the drone's charge was $2500$ mAh.

Solve
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Find the function $f(x)$ that satisfies the condition of being continuous over the entire domain of definition of its branches, given that its derivative is given by:…

Find the function $f(x)$ that satisfies the condition of being continuous over the entire domain of definition of its branches, given that its derivative is given by:

$$f'(x) = \begin{cases} \frac{1}{x^2+1} & \text{if } x \leq 0 \\ x \cdot e^x & \text{if } x > 0 \end{cases}$$

and that $f(1) = 1$. You will need to integrate the second branch by parts and determine the value of the constants of integration to guarantee continuity at $x = 0$.

Solve

Rates, velocity and position

Back to the start: the data arrives at rate $v(t) = \frac{4}{t+1}$ GB per minute, so the amount stored is $S(t) = \int\frac{4}{t+1}\,dt = 4\ln(t+1) + C$. Here $t + 1 > 0$, so no absolute value is needed, and the constant $C$ is the amount stored at $t = 0$ (since $\ln 1 = 0$). That is the idea in every "rate $\to$ total" problem. In motion problems the same idea chains twice: acceleration $\to$ velocity $\to$ position.

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A group of young engineers is monitoring the data flow of a server. The growth rate of stored data (in GB/min) is given by the function $v(t) = \frac{4}{t + 1}$, where…

A group of young engineers is monitoring the data flow of a server. The growth rate of stored data (in GB/min) is given by the function $v(t) = \frac{4}{t + 1}$, where $t$ is the time in minutes. Obtain the general expression for the data storage function $S(t)$.

4 2 1 3 0 t (min) v(t) (GB/min) t S(t) v(t) = 4/(t+1)
Solve
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An object moves along a straight line with a time-dependent acceleration defined by $a(t) = \ln(t+1)$. If at the initial time ($t=0$) the object was at rest and at the…

An object moves along a straight line with a time-dependent acceleration defined by $a(t) = \ln(t+1)$. If at the initial time ($t=0$) the object was at rest and at the position $s=10$ feet, determine the equation of the position $s(t)$ at any time $t$.

Note: Remember that velocity is the integral of acceleration and position is the integral of velocity. Both integrals require the use of the method of integration by parts.

Solve
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It is known that the acceleration of a particle moving in a straight line is defined by the expression $a(t) = t \cdot \sin(t)$ for $t \geq 0$. Determine the velocity…

It is known that the acceleration of a particle moving in a straight line is defined by the expression $a(t) = t \cdot \sin(t)$ for $t \geq 0$.

Determine the velocity function $v(t)$, given that at time $t = \pi$ the velocity of the particle is $2$ ft/s.

t a(t) 0 π/2 π 3π/2 a(t) a(t) = t·sin(t) v(π) = 2 m/s v(t) = ?
Solve

Summary

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