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# Integration Formula

There are two sides to the mighty coin of calculus: Derivatives and Integrals. There is a whole study set for the former one, but this one goes to the latter one. The idea of an integral has been made pretty clear and explicit by now.

But we cannot forget formulas, the very basis of mathematics. Integration is littered with a multitude of distinct formulas, which makes it an easy task to do an integral, partly.

Let's take a look at some of these Integration Formulas:

## Integration Formula definition

It might sound absurd at first, that we can have formulas for integrals straight away. But there is a catch, we can only have formulas for relatively simple integrals, not for more composite functions.

Let us start with the very basics, the fundamental formulas of integration:

### Basic Integration formulas

The following formulas we are going to talk about, are the very fundamental formulas, upon which other formulas are eventually built.

Hence, it would be a good practice to remember them by heart:

\begin{aligned} &\int x^n \, \mathrm{d}x = \frac{x^{n+1}}{n+1}+c \\ &\int e^x \, \mathrm{d}x=e^x+c \\ &\int a^x \, \mathrm {d}x=\frac{a^x}{\log_e a}+c \\&\int \frac{1}{x} \, \mathrm{d}x=\log_e x +c \end{aligned}

## Integration formulas of Trigonometric Functions

We just saw integration formulas for functions such as the linear function, quadratic functions, exponential function, logarithmic functions, and also functions like $$\frac{1}{1+x}, \ \frac{1}{1+x^2}$$ and so on.

But there is a whole class of important functions that we have not addressed yet, the Trigonometric Functions. There are some basic formulas one needs to remember for trigonometric functions, from which we can solve more complicated trigonometric functions. These Integration formulas are as follows:

\begin{aligned} &\int \cos x \, \mathrm{d}x=\sin x+c \\ &\int \sin x \, \mathrm{d}x=-\cos x+c \\ &\int \tan x \, \mathrm{d}x=-\log_e |\cos x|+c \\ &\int \cot x \, \mathrm{d}x=\log_e |\sin x|+c \\ &\int \sec^2 x \, \mathrm{d}x=\tan x +c \\ &\int \csc x \, \mathrm{d}x=\log_e |\frac{\tan x}{2}|+c \\ &\int \sec x \tan x \, \mathrm{d}x=\sec x+c \\ &\int \csc^2 x \, \mathrm{d}x=-\cot x+c \\ &\int \csc x \cot x \, \mathrm{d}x=-\cot x+c \end{aligned}

You might wonder why there is a constant of integration at the end of every indefinite integral. The reason is that if we take the derivative of the result we get, the constant disappears, this is because the derivative is the opposite of an integral.

## Definite integral formula

As you may have noticed, the integration we saw are all related to indefinite integrals. But what about definite integrals? The integrals of all the functions remain unchanged, the only thing introduced are the limits of integration.

Below are some formulas, properties essentially, that are crucial while doing definite integration.

\begin{aligned} &\int_a^b f(x) \, \mathrm{d}x=F(b)-F(a) \ ; \text{where} \ \int f(x) \, \mathrm{d}x=F(x)+c \\ &\int_a^b f(x) \, \mathrm{d}x=-\int_b^a f(x) \, \mathrm{d}x \\ &\int_a^b f(x) \, \mathrm{d}x=\int_a^b f(a+b-x) \, \mathrm{d}x \\ &\int_{-a}^a f(x) \, \mathrm{d}x=2\int_0^a f(x)\, \mathrm{d}x\ ; \text{where} \ f(x) \ \text{is an even function} \\ &\int_{-a}^a f(x) \, \mathrm{d}x=0 \ ; \text{where} \ f(x) \ \text{is an odd function} \\ \end{aligned}

Notice that there is no constant of integration in definite integration.

## Integration formula Chart

While solving integrals, we need to know a multitude of different integration formulas, without which, solving integrals will be impossible (unless you cheat using WolframAlpha or something!).

Below is a list of almost all the integration formulas one shall need in order to solve more complicated integrals, which comprise different composite functions. This will include formulas you already saw earlier (trigonometric, fundamental) alongside inverse trigonometric formulas, hyperbolic formulas, and many more. It is a handy chart one should have while doing integrals:

### Fundamental Integration Formulas chart

Let us revisit some of the fundamental integration formulas as a chart:

\begin{aligned} &\int x^n\, \mathrm{d} x=\frac{x^{n+1}}{n+1}+c \\ &\int e^x \, \mathrm{d}x=e^x+c \\ &\int a^x \, \mathrm{d}x=\frac{a^x}{\log_e a}+c \\ &\int \frac{1}{x} \, \mathrm{d}x=\log_e x +c \\ &\int k\, \mathrm{d} x=k x+c \end{aligned}

### Inverse Trigonometric Integration Chart

Below is the chart for integrals of inverse trigonometric functions:

\begin{aligned} &\int \sin^{-1} x \, \mathrm{d} x=x \sin^{-1} x+\sqrt{1-x^2}+c \\&\int \cos^{-1} x \, \mathrm{d} x=x \cos^{-1} x-\sqrt{1-x^2}+c \\&\int \tan^{-1} x \, \mathrm{d} x=x \tan^{-1} x-\frac{1}{2} \ln \left(x^2+1\right) +c\\&\int \cot^{-1} x \, \mathrm{d} x=x \cot^{-1} x+\frac{1}{2} \ln \left(x^2+1\right) +c\\ &\int \csc ^{-1} x \, \mathrm{d} x=x \csc ^{-1} x+\ln \left|x+\sqrt{x^2-1}\right|+c \\ &\int \sec ^{-1} x \, \mathrm{d} x=x \sec ^{-1} x-\ln \left|x+\sqrt{x^2-1}\right|+c \end{aligned}

### Other Integration formulas chart

There are some other integration formulas, which are listed below: \begin{aligned} &\int e^{c x} \sin b x \, \mathrm{d} x=\frac{e^{c x}}{c^2+b^2}(c \sin b x-b \cos b x) +c\\ &\int e^{c x} \cos b x \, \mathrm{d} x=\frac{e^{c x}}{c^2+b^2}(c \cos b x+b \sin b x) +c\\&\int \frac{1}{x^2+a^2} \, \mathrm{d} x=\frac{1}{a} \tan^{-1} \frac{x}{a} +c\\&\int \frac{1}{x^2-a^2} \, \mathrm{d} x= \left\{\begin{array}{l} \displaystyle \frac{1}{2 a} \ln \left( \frac{a-x}{a+x} \right) +c\\\displaystyle \frac{1}{2 a} \ln \left( \frac{x-a}{x+a} \right)+c \end{array}\right. \end{aligned}

### Trigonometric Integration formulas Chart

Let us revisit the trigonometric formulas with some squared formulas and hyperbolic formulas as well:

\begin{aligned} &\int \sin x \, \mathrm{d} x=-\cos x+c \\&\int \cos x \, \mathrm{d} x=\sin x+c \\&\int \tan x \, \mathrm{d} x=\ln |\sec x|+c \\&\int \sec x \, \mathrm{d} x=\ln |\tan x+\sec x|+c \\&\int \sin ^2 x \, \mathrm{d} x=\frac{1}{2}(x-\sin x \cos x)+c \\&\int \cos ^2 x \, \mathrm{d} x=\frac{1}{2}(x+\sin x \cos x)+c \\&\int \tan ^2 x \, \mathrm{d} x=\tan x-x+c \\&\int \sec ^2 x \, \mathrm{d} x=\tan x+c \\ &\int \sin x \cos ^n x \, \mathrm{d} x=-\frac{\cos ^{n+1} x}{n+1}+c \\ &\int \sin ^n x \cos x \, \mathrm{d} x=\frac{\sin ^{n+1} x}{n+1} +c\\&\int \sinh x \, \mathrm{d}x=\cosh x +c \\ &\int \cosh x \, \mathrm{d}x=\sinh x +c\end{aligned}

Some of the above formulas are themselves derived from the other ones, we take them as formulas since they appear quite often while solving integrals.

## Examples of Integration Formula

Now let us apply these formulas and solve a couple of integrals. We shall use the above formulas without providing their proof, unless we are asked to provide one specifically.

Solve the indefinite integral $$\displaystyle \int \cos 4x \, \mathrm{d}x$$.

Solution:

Recall that $$\int \cos x \, \mathrm{d}x=\sin x+c$$, we get here:

$$\int \cos 4x \, \mathrm{d}x= \frac{\sin 4x}{4}+c \ \ \ \ \ (\because \int f(ax)\, \mathrm{d}x=\frac{F(ax)}{a}+c)$$

Evaluate the definite integral $$\displaystyle \int_0^1 (x+1)^2 \, \mathrm{d}x$$.

Solution:

Here first we will integrate it as we normally would, and then apply the limits of integration using the property of definite integration ($$\int_a^b f(x) \, \mathrm{d}x=F(b)-F(a)$$).

Using the formula $$\displaystyle \int x^n \, \mathrm{d}x=\frac{x^{n+1}}{n+1}+c$$,

\begin{aligned} \int_0^1 (x+1)^2 \, \mathrm{d}x &=\left[\frac{(x+1)^3}{3} \right]_0^1 \\ &=\frac{(1+1)^3}{3}-\frac{(0+1)^3}{3} \\ &=\frac{8-1}{3} \\ \therefore \int_0^1 (x+1)^2 \, \mathrm{d}x &=\frac{7}{3} \end{aligned}

Evaluate the integral $$\int \cos^2 x \, \mathrm{d}x$$.

Solution:

Firstly, we shall use the double-angle trigonometric identity $$\cos^2 x=\frac{1+\cos 2x}{2}$$:

$$\int \cos^2 x \, \mathrm{d}x=\int \frac{1+\cos 2x}{2} \, \mathrm{d}x$$

Now, using the integral formulas $$\int x^n \, \mathrm{d}x=\frac{x^{n+1}}{n+1}+c$$ and $$\int \cos x \, \mathrm{d}x=\sin x+c$$:

\begin{aligned} \int \cos^2 x \, \mathrm{d}x &=\int \frac{1+\cos 2x}{2} \, \mathrm{d}x \\ &=\frac{x}{2}+\frac{\sin 2x}{4}+c \end{aligned}

Evaluate the integral $$\int_{-\pi}^{\pi} \sec x \tan x \, \mathrm{d}x$$.

Solution:

Notice that the limits of integration are of the form $$-a$$ to $$a$$, which means we should first check whether the given function is even or odd.

\begin{aligned} f(-x) &=\sec (-x) \tan (-x) \\ &=-\sec x \tan x \\ \therefore f(-x) &=-f(x) \end{aligned}

Hence, the function is an odd function. So we shall use the property of the definite integral: $$\int_{-a}^a f(x) \, \mathrm{d}x = 0$$.

Thus,

$$\int_{-\pi}^{\pi} \sec x \tan x \, \mathrm{d}x =0$$

Evaluate $$\int_{\pi / 3}^{\pi / 2} x \sin x\, \mathrm{d} x$$

Solution:

Notice that we have the integrand as a product of two functions, so we have to use integration by parts:

\begin{align} &u=x \ \, \, \text{and} \, \, \mathrm{d} v=\sin x \, \mathrm{d}x \\ &\, \mathrm{d}u= \mathrm{d} x \, \, \ \text{and} \quad v=-\cos x \end{align}

which yields

\begin{aligned} \int x \sin x \, \mathrm{d}x &=-x \cos x-\int-\cos x \, \mathrm{d}x \\ &=-x \cos x+\sin x+c \end{aligned}

Hence,

\begin{aligned} \int_{\pi / 3}^{\pi / 2} x \sin x \, \mathrm{d}x &=[-x \cos x+\sin x]_{\pi / 3}^{\pi / 2} \\ &=\left[\left(-\frac{\pi}{2}\right)\left(\cos \frac{\pi}{2}\right)+\sin \frac{\pi}{2}\right]-\left[\left(-\frac{\pi}{3}\right)\left(\cos \frac{\pi}{3}\right)+\sin \frac{\pi}{3}\right] \\ &=(0+1)-\left(-\frac{\pi}{6}+\frac{\sqrt{3}}{2}\right) \\ &=1+\frac{\pi}{6}-\frac{\sqrt{3}}{2} \\ &=\frac{6-3 \sqrt{3}+\pi}{6} \end{aligned}

## Integration Formulas - Key takeaways

• There are a bunch of formulas that are essential to integration, which form the fundamentals to solving other integrals.
• There are some fundamental integration formulas such as $$\int x^n \, \mathrm{d}x=\frac{x^{n+1}}{n+1}+c, \ \int e^x \, \mathrm{d}x =e^x+c, \ \int \frac{1}{x} \, \mathrm{d}x=\log_e x+c$$ which build up to more complex polynomial integrals and exponential integrals.
• Trigonometric integral formulas are essential for composite trigonometric integrals, they are as follows: \begin{aligned} &\int \cos x \, \mathrm{d}x=\sin x+c, \ \int \sin x \, \mathrm{d}x=-\cos x+c, \\ &\int \tan x \, \mathrm{d}x=-\log_e |\cos x|+c, \ \int \cot x \, \mathrm{d}x=\log_e |\sin x|+c, \\ & \int \sec^2 x \, \mathrm{d}x=\tan x +c, \ \int \csc x \, \mathrm{d}x=\log_e |\frac{\tan x}{2}|+c, \\ &\int \sec x \tan x \, \mathrm{d}x=\sec x+c, \ \int \csc^2 x \, \mathrm{d}x=-\cot x+c, \\ &\int \csc x \cot x \, \mathrm{d}x=-\cot x+c \end{aligned}
• These formulas remain unchanged in the case of Definite integrals, and the only thing that is added is the limits of integration. Although, some properties need to be remembered.

The 3 basic integration methods are Integration by Substitution, Integration by Parts and Direct Integration.

Basic integration involves the three basic integration techniques alongside the basic integration formulas.

The integral of dx is x+c where c is a constant.

Integration is the opposite operation of taking a derivative, the derivative of a constant disappears, so we need to add it back when we integrate the function.

The rules of integration are quite basic, following the integration formulas and using the three basic integration methods, and applying the laws of definite integration when the limits are given.

## Final Integration Formula Quiz

Question

Even functions are also known as:

Symmetric functions.

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Question

Odd functions are also known as:

Antisymmetric functions.

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Question

Let $$f$$ be an even function that is integrable over the interval $$[-a,a]$$. Which of the following formulas holds true?

$$\int_{-a}^a f(x) \, \mathrm{d}x=2\int_0^a f(x)\, \mathrm{d}x.$$

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Question

Find the value of $$\int_{-1}^1 10x^{4}+6x^{2}+1 \, \mathrm{d}x$$.

$$10$$.

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Question

Find the value of $$\int_{-3}^3 (x^7-5x^5+3x^3+x) \, \mathrm{d}x$$.

$$0$$.

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Question

Find the value of $$\int_{-\pi}^{\pi} \sin x \, \mathrm{d}x$$.

$$0$$.

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Question

Find the value of $$\int_{\pi/2}^{-\pi/2} \cos x \, \mathrm{d}x$$.

$$-2$$.

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Question

Which of the following can be used to prove the net change theorem?

The Fundamental Theorem of Calculus

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Question

Suppose you know $$F(b)$$ and the value of $$\int_a^b F'(x) \, \mathrm{d}x$$. Can you find $$F(a)$$ using this information?

Yes.

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Question

Which of the following is not an accumulation function?

$\int_1^2 t^2 \, \mathrm{d}t$.

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Question

An accumulation function is a function obtained by solving a definite integral while leaving one of the ____ as a variable.

integration limits.

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Question

True/False: The variable of an accumulation function has to be the upper integration limit.

False.

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Question

True/False: The variable of an accumulation function can be the lower integration limit.

True.

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Question

True/False: Given a function $$f(t)$$ and an interval $$[a,b]$$, you can define more than one accumulation function.

True.

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Question

To find an accumulation function you need to solve a(n) ____.

definite integral.

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Question

Which of the following is not an accumulation function?

$\int_{-2}^2 t^2 \, \mathrm{d}t$.

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Question

Solving the definite integral
$\int_2^8 t \, \mathrm{d}t$
will give you a ____ .

number.

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Question

Solving the definite integral
$\int_0^4 (t-1) \,\mathrm{d}t$
will give you ____.

$$4$$.

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Question

Solving the definite integral
$\int_1^t e^x \, \mathrm{d}x$
will give you a ____.

function of $$t$$.

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Question

True/False: The value of
$\int_1^2 y^7 \, \mathrm{d}y$
is the same as the value of
$\int_1^2 t^7 \, \mathrm{d}t$.

True.

Show question

Question

True/False: The value of
$\int_1^5 2^x \, \mathrm{d}x$
is the same as the value of
$\int_1^5 t^2 \, \mathrm{d}t$.

False.

Show question

Question

Consider the integral
$\int_1^x e^t \, \mathrm{d}t$.
Which is the integration variable?

$$t$$.

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Question

Consider the integral
$\int_y^8 x^2 \, \mathrm{d}x.$
The variable $$y$$ is ____.

an integration limit.

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Question

True/False: Consider the function $$f(t)$$. Any accumulation function using $$f(t)$$ as the integrand will result in an antiderivative of $$f$$.

False.

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Question

True/False: Define an accumulation function as
$F(x)= \int_a^x f(t)\,\mathrm{d}t.$
$$F(x)$$ and $$f(x)$$ have the same graph.

False.

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Question

True/False: Define an accumulation function as

$F(x)= \int_a^x f(t)\,\mathrm{d}t.$

$$F'(x)$$ and $$f(x)$$ have the same graph.

True.

Show question

Question

Consider the function
$G(x)= \int_2^x f(t)\,\mathrm{d}t.$
$$G(4)$$ is equal to ____.

the area below $$f$$ in the interval from $$2$$ to $$4$$.

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Question

Is the following integral correct?

$$\int e^x \, \mathrm{d}x=\frac{e^{x+1}}{x+1}+c$$

No.

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Question

Evaluate the integral $$\int \sin^2 x \, \mathrm{d}x$$.

$$\int \sin^2 x \, \mathrm{d}x= \frac{x}{2}-\frac{\sin 2x}{4}+c$$

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Question

Evaluate the integral $$\int \log_e x \, \mathrm{d}x$$

$$\int \log_e x \, \mathrm{d}x= x\log_e x-x+c$$

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Question

Solve the integral $$\int_{-b}^b x \, \mathrm{d}x$$ without actually calculating it.

$$\int_{-b}^b x \, \mathrm{d}x=0$$ since $$x$$ is an odd function.

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Question

Is the integral $$\int \tan^{-1} y \, \mathrm{d}x=\frac{1}{1+x^3}+c$$ true?

No.

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Question

What is the integral $$\int_1^2 \frac{1}{x^2} \, \mathrm{d}x$$?

$$\frac{1}{2}$$.

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