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Integrals · Antiderivatives

Antiderivative and Indefinite Integral

Before you start, make sure you know: Derivatives of common functions (High School Year 2 (semesters 3 and 4))
Before you start, make sure you know: Differentiation rules (High School Year 2 (semesters 3 and 4))

A surveillance drone flies over the Alameda in Querétaro, and your phone records its velocity at every instant. How do you recover where the drone is from that velocity? Until now you went from $f$ to $f'$. Now the problem is reversed: you are given $f'$ and have to recover $f$. It is the same table of derivatives, read backward.

Differentiating backward: what an antiderivative is

If $s(t)$ is the position and $v(t)=s'(t)$ the velocity, knowing $v(t)$ and wanting to recover $s(t)$ is exactly this problem. In the section on the Fundamental Theorem you will see why integrating and differentiating are inverse operations.

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Determine whether the function $F(x) = x \times e^x$ is an antiderivative of the function $f(x) = (x+1)e^x$. To justify your answer, remember to use the fundamental…

Determine whether the function $F(x) = x \times e^x$ is an antiderivative of the function $f(x) = (x+1)e^x$. To justify your answer, remember to use the fundamental relationship between a function and its antiderivative via differentiation.

Solve

Infinitely many antiderivatives: the constant $C$

Family of antiderivatives: parallel curves shifted vertically by the constant C F(x) F(x)+C₁ F(x)+C₂

To pick one antiderivative you only need one extra piece of data: the value of $F$ at a point (an initial condition).

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Find the antiderivative of the function $f(x) = 2x - 6$ whose graph passes through the point $P(3, 4)$. Note: First calculate the indefinite integral to obtain the…

Find the antiderivative of the function $f(x) = 2x - 6$ whose graph passes through the point $P(3, 4)$.

Note: First calculate the indefinite integral to obtain the family of functions with the constant $C$, and then use the point $P$ to find the specific value of that constant.

Solve
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A surveillance drone moves such that its horizontal velocity (in m/s) is given by the function $v(t) = 4e^{2t-1} + \sin(3t)$. Given that at the initial instant $t=0$ the…

A surveillance drone moves such that its horizontal velocity (in m/s) is given by the function $v(t) = 4e^{2t-1} + \sin(3t)$. Given that at the initial instant $t=0$ the drone is at position $s=0$, determine the expression for the position function $s(t)$.

s (m) s₀ = 0 t = 0 s(t) = ? t > 0 v(t) s(t) = ∫ v(t) dt v(t) = 4e²ᵗ⁻¹ + sin(3t)
Solve

The table of derivatives, read backward

Each differentiation rule, read from right to left, gives a basic integral. There is nothing new to memorize.

Diagram showing that the table of integrals is the table of derivatives read in reverse: differentiating goes down, integrating goes up ∫xⁿ dx = xⁿ⁺¹/(n+1)+C differentiate (↓) integrate (↑): read backward (xⁿ⁺¹/(n+1))' = xⁿ
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In a study on how news spreads on a social network, it was determined that the growth rate of "shares" follows a power law. To find the cumulative total, a programmer…

In a study on how news spreads on a social network, it was determined that the growth rate of "shares" follows a power law. To find the cumulative total, a programmer must solve the following integral of an irrational function. Calculate it by first expressing the root as a fractional exponent:

$$\int \left( \sqrt[3]{x^2} + \frac{1}{\sqrt{x}} \right) \, dx$$
Solve
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Find all antiderivatives of the function $f(x) = \frac{x^4 - 2x^2 + 5}{x^2}$.

Find all antiderivatives of the function $f(x) = \frac{x^4 - 2x^2 + 5}{x^2}$.

Solve
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Find the family of antiderivatives of the following function, simplifying the result by eliminating negative exponents and using radicals:…

Find the family of antiderivatives of the following function, simplifying the result by eliminating negative exponents and using radicals:

$f(x) = \dfrac{3}{x^4} - \dfrac{2}{\sqrt[3]{x^2}} + \dfrac{1}{5x}$

x y + C - C F(x) + C₁ F(x) + C₂ F(x) + C₃ ∫ f(x)dx = F(x) + C
Solve

Linearity: sums, differences, and constants

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Calculate the indefinite integral of the following combination of trigonometric functions and constants, applying linearity properties (factoring out constants and…

Calculate the indefinite integral of the following combination of trigonometric functions and constants, applying linearity properties (factoring out constants and splitting sums):

$$\int (4 \sin x - 5 \cos x + 3) \, dx$$ 0 x y f(x) = 4sin(x) - 5cos(x) + 3 ∫ f(x) dx
Solve
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A hearing study for teenagers analyses the intensity of a sound signal. The function describing the instantaneous sound pressure is $p(x) = \frac{3}{x} + e^{2x}$. Find…

A hearing study for teenagers analyses the intensity of a sound signal. The function describing the instantaneous sound pressure is $p(x) = \frac{3}{x} + e^{2x}$. Find the general antiderivative of this function by carrying out the integration:

$$\int \left( \frac{3}{x} + e^{2x} \right) \, dx$$
Solve
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In the design of a smartphone camera lens, the curvature function needs to be known. The derivative of this function is $g'(x) = \frac{7}{1 + x^2} - 2^x$. Obtain the…

In the design of a smartphone camera lens, the curvature function needs to be known. The derivative of this function is $g'(x) = \frac{7}{1 + x^2} - 2^x$. Obtain the expression for the function $g(x)$ by evaluating its indefinite integral:

$$\int \left( \frac{7}{1+x^2} - 2^x \right) \, dx$$
Solve

Adjusting for the inner derivative and dividing first

Many integrals seem not to be basic, but they are after an adjustment.

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Find the indefinite integral of the function $g(x)$, making the necessary constant adjustments to obtain a logarithmic form:…

Find the indefinite integral of the function $g(x)$, making the necessary constant adjustments to obtain a logarithmic form:

$I = \displaystyle\int \dfrac{3x - 1}{x^2 - \frac{2}{3}x + 5} \, dx$

Solve
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Find the antiderivative of the function $f(x) = \dfrac{x^2 - 4x + 1}{x-2}$ whose graph passes through the point $P(3, 5)$. Note: Perform polynomial division first.

Find the antiderivative of the function $f(x) = \dfrac{x^2 - 4x + 1}{x-2}$ whose graph passes through the point $P(3, 5)$.

Note: Perform polynomial division first.

Solve
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Determine the indefinite integral of the following composite function, identifying the derivative of the inner function:…

Determine the indefinite integral of the following composite function, identifying the derivative of the inner function:

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

Solve

Completing the square: arctangent and arcsine

When the denominator is a degree-2 polynomial with no real roots, the result is an arctangent. First you have to bring it to the form $u^2+a^2$.

To complete the square: $x^2+bx+c=\left(x+\frac b2\right)^2+\left(c-\frac{b^2}{4}\right)$.

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Calculate the indefinite integral of the following function using linearity decomposition and adjusting for the derivative of the exponent:…

Calculate the indefinite integral of the following function using linearity decomposition and adjusting for the derivative of the exponent:

$I = \displaystyle\int \left( 2x \times e^{x^2+3} - \dfrac{5}{1+4x^2} \right) \, dx$

∫y₁dx ∫y₂dx f(x) = y₁ + y₂ y₂ = −5/(1+4x²) ↳ 4x² = (2x)² y₁ = 2x·eˣ²⁺³ ↳ 2x = (x²⁺³)'
Solve
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Find the indefinite integral of the following rational function by completing the square in the denominator to identify an arctangent form: $$f(x) = \frac{3}{2x^2 - 4x +…

Find the indefinite integral of the following rational function by completing the square in the denominator to identify an arctangent form:

$$f(x) = \frac{3}{2x^2 - 4x + 10}$$
Solve
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A logistics company studies the tire wear of its fleet. The wear rate $V(x)$ (in mm per 1000 km) depends on the load $x$ (in metric tons) according to the function:…

A logistics company studies the tire wear of its fleet. The wear rate $V(x)$ (in mm per 1000 km) depends on the load $x$ (in metric tons) according to the function:

Graphical interpretation of accumulated wear D(x) as the area under the wear rate curve V(x)x = 1x = 51234501234x5D(3) = 0Load x (metric tons)Wear rate V(x) (mm/1000 km)V(x)D(x)Accumulated wear

$V(x) = \frac{x + 1}{\sqrt{4 - (x - 3)^2}}$

Find the accumulated wear function $D(x)$, knowing that for a load of $3$ metric tons ($x = 3$) the wear is zero.

Solve

Trigonometric identities for integrating

Sometimes the integrand is not in the table, but an identity turns it into a sum of basic integrals.

Also, $\int \sec^2(kx)\,dx=\frac1k\tan(kx)+C$ (chain rule in reverse).

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Given the function $f(x) = \dfrac{\sin(x)}{\sqrt{1 + \cos(x)}}$, calculate its general antiderivative. Check your result by differentiating the obtained function.

Given the function $f(x) = \dfrac{\sin(x)}{\sqrt{1 + \cos(x)}}$, calculate its general antiderivative. Check your result by differentiating the obtained function.

Solve
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Find the antiderivative $F(x)$ of the function $f(x) = \dfrac{1}{\cos^2(3x)} + 5^{2x}$ knowing that $F(0) = 1$.

Find the antiderivative $F(x)$ of the function $f(x) = \dfrac{1}{\cos^2(3x)} + 5^{2x}$ knowing that $F(0) = 1$.

Solve
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Find the family of antiderivatives of the following trigonometric function using fundamental identities to transform the integrand into a sum of standard integrals:…

Find the family of antiderivatives of the following trigonometric function using fundamental identities to transform the integrand into a sum of standard integrals:

$$f(x) = \frac{\cos^3 x}{\sin^4 x}$$
Solve

Piecewise functions and absolute value

If $f$ is defined piecewise (or has $|\cdot|$), integrate each piece with its own constant. But an antiderivative is differentiable, so it must be continuous: the constants are adjusted so that the pieces connect.

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Given the function $f(x) = |x - 2| \times e^x$, find the antiderivative $F(x)$ satisfying $F(0) = 1$. Remember that for $F(x)$ to be an antiderivative on its entire…

Given the function $f(x) = |x - 2| \times e^x$, find the antiderivative $F(x)$ satisfying $F(0) = 1$.

Remember that for $F(x)$ to be an antiderivative on its entire domain, it must be a continuous function, so you will need to adjust the constants of integration across the different intervals.

Solve
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Determine the values of the parameters $A, B$, and $C$ such that the function $F(x) = (Ax^2 + B) \sin(2x) + Cx \cos(2x)$ is an antiderivative of $f(x) = x^2 \cos(2x)$.…

Determine the values of the parameters $A, B$, and $C$ such that the function $F(x) = (Ax^2 + B) \sin(2x) + Cx \cos(2x)$ is an antiderivative of $f(x) = x^2 \cos(2x)$.

Set up the system of equations by differentiating $F(x)$ and equating coefficients.

Solve

Combined challenges

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A sound engineer is analysing the signal of a new synthesiser. The rate of change of the wave intensity with respect to time, $t$, is given by the function…

A sound engineer is analysing the signal of a new synthesiser. The rate of change of the wave intensity with respect to time, $t$, is given by the function $f'(t) = \dfrac{e^{2t} + 3e^t}{e^t + 1}$.

Knowing that for a time $t = 0$ the intensity of the wave is $10$ units, determine the algebraic expression for the intensity $f(t)$ by performing the necessary algebraic manipulations to solve the integral.

Time (t) Intensity f'(0) = 2 f(0) = 10 f(t) = ? 1 2 3 4 5 10 20 30 40 f'(t) = e2t+ 3et et + 1
Solve
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Determine the function $f(x)$ whose second derivative is $f''(x) = \dfrac{12x^2 - 4}{(x^2 + 1)^3}$. It is known that the graph of $f(x)$ has an inflection point with…

Determine the function $f(x)$ whose second derivative is $f''(x) = \dfrac{12x^2 - 4}{(x^2 + 1)^3}$.

It is known that the graph of $f(x)$ has an inflection point with positive $x$-coordinate at which the tangent line is horizontal, and that the graph of $f(x)$ passes through the point $(0, 5)$.

Note: This exercise requires an expert handling of the chain rule in reverse for rational functions.

Solve
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Calculate the indefinite integral of the function: $$f(x) = \frac{\ln(\ln x)}{x \times \ln x}$$ This exercise assesses the ability to recognize the structure…

Calculate the indefinite integral of the function:

$$f(x) = \frac{\ln(\ln x)}{x \times \ln x}$$

This exercise assesses the ability to recognize the structure $g(u(x)) \times u'(x)$ when there are multiple composite functions.

Solve

Summary

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