# Integral Of Sin^3x Cos X

Integral of sin^3x * cos x along with its formula and proof with examples. Also learn how to calculate integration of sin^3x * cos x with step by step examples.

Alan Walker-

Published on 2023-04-13

## Introduction:

The integral of Sin^3x Cos X is a mathematical problem that involves finding the antiderivative of the product of Sin^3x and Cos X functions. This integral is widely used in calculus and physics problems. In this article, we will explore the definition of this integral, its importance, and methods for solving it.

## Definition of Integral of Sin^3x Cos X:

The integral of Sin^3x Cos X can be defined as the antiderivative of the product of the Sin^3x and Cos X functions. Mathematically, it can be represented as:

∫ Sin^3x Cos X dx

## Importance of Learning how to Solve this Integral:

The integral of Sin^3x Cos X has several applications in real-world problems, particularly in physics and engineering. By learning how to solve this integral, you can solve various calculus problems related to acceleration, velocity, and position. Moreover, it can help you in solving complex trigonometric equations and identities.

## Methods for Solving the Integral of Sin^3x Cos X:

There are different methods for solving the integral of Sin^3x Cos X, which are discussed below:

### a. Integration by Parts Method:

The integration by parts method involves choosing one function as u and the other as dv, and then applying the integration formula. For the integral of Sin^3x Cos X, we can choose Sin^3x as u and Cos X dx as dv.

### b. Trigonometric Substitution Method:

The trigonometric substitution method involves substituting a trigonometric expression for x in the integrand. For the integral of Sin^3x Cos X, we can use the substitution x = Sin θ.

### c. Reduction Formula Method:

The reduction formula method involves using a formula to reduce the power of a trigonometric function in the integrand. For the integral of Sin^3x Cos X, we can use the reduction formula for Sin^nx.

## Step-by-Step Solutions for the Integral of Sin^3x Cos X:

We will now provide step-by-step solutions for the integral of Sin^3x Cos X using the methods mentioned above.

### Integration by Parts Method:

Integration by parts finder is another method for solving the integral of sin^3x cos x. It is used when the integrand can be written as a product of two functions. The integration by parts formula is given as:

∫u dv = uv − ∫v du

where u and v are functions, and du and dv are their differentials.

To use the integration by parts method for the integral of sin^3x cos x, we can choose u = sin^2x and dv = cos x dx. This gives us du = 2sin x cos x dx and v = sin x.

Substituting these values into the integration by parts formula, we get:

∫sin^3x cos x dx = ∫u dv = uv − ∫v du

= sin^2x sin x − ∫sin x (2sin x cos x dx)

= sin^3x − 2∫sin^2x cos x dx

Now we can use another integration by parts formula with u = sin x and dv = cos x dx. This gives us du = cos x dx and v = sin x. Substituting these values, we get:

∫sin^3x cos x dx = sin^3x − 2∫sin^2x cos x dx

= sin^3x − 2(uv − ∫v du)

= sin^3x − 2sin x cos x + 2∫cos^2x dx

= sin^3x − 2sin x cos x + 2∫(1 − sin^2x) dx

= sin^3x − 2sin x cos x + 2x − (2/3)sin^3x + C

where C is the constant of integration.

Using the integration-by-parts method can be useful for evaluating integrals where the product of functions is not easily simplified using trigonometric identities or substitution. Similarly, this method is also helpful to solve the sin(mx)cos(nx) integration

### Trigonometric Substitution Method:

Trigonometric substitution is another method that can be used to find the integral of sin^3x cos x. This method involves using a substitution that converts the integrand into a simpler form that can be easily integrated.

The first step in this method is to identify a substitution of the form u = sin(x) or u = cos(x) that can simplify the integrand. For instance, if we choose u = sin(x), then we can express the cosine term in terms of sin(x) using the identity cos^2(x) = 1 - sin^2(x). This yields:

sin^3(x) cos(x) = sin^2(x) cos(x) sin(x) = (1 - cos^2(x)) cos(x) sin(x) = (1 - u^2) du

We can then substitute this expression into the integral, which gives us:

∫ sin^3(x) cos(x) dx = ∫ (1 - u^2) du

The integral on the right-hand side is now a simple polynomial, which can be easily integrated to obtain the final solution:

∫ sin^3(x) cos(x) dx = (-1/4) cos^2(x) (2 sin(x) + cos(x)) + C

where C is the constant of integration. The above method is also known as u substitution method because we replace a function with a parameter u. Use our u-substitution calculator to evaluate integrals by writing them in simpler form.

Trigonometric substitution can be a powerful method for solving integrals that involve trigonometric functions, and it is particularly useful when the integrand contains powers of sin(x) and cos(x). However, it can be somewhat tricky to apply in practice, and it may require some algebraic manipulation to simplify the integrand before the substitution can be made.

### Reduction Formula Method:

The reduction formula method is another approach to finding the integral of sin^3x cosx. This method involves using a formula that relates the integral of sin^n x cos x to the integral of sin^(n-1) x cos^2 x.

The formula is as follows:

∫sin^n x cos x dx = -(1/n) sin^(n-1) x cos x + (n-1)/n ∫sin^(n-2) x dx

Using this formula repeatedly, we can reduce the power of sin in the integrand until we reach an integral that can be easily evaluated.

To use the reduction formula method, we first rewrite sin^3x as sin^2x * sinx. We can then use the formula above with n=3 to find the integral of sin^2x * sinx cosx. We get:

∫sin^3 x cos x dx = -(1/3) sin^2 x cos x + (2/3) ∫sin x dx

We can then use the formula again with n=1 to find the integral of sin x, which is easy to evaluate. We get:

∫sin x dx = -cos x + C

Substituting this back into the first equation, we get:

∫sin^3 x cos x dx = -(1/3) sin^2 x cos x - (2/3) cos x + C

This is the final solution to the integral of sin^3x cosx using the reduction formula method. This method is useful to evaluate integrals with some power. For example, to solve the integration of sin^4xcos^2x we need to write it is a simpler form by using reduction method.

## Applications of the Integral of Sin^3x Cos X

The integral of sin^3x cos x is a mathematical operation used to find the antiderivative of the function sin^3x cos x with respect to the variable x. This operation is relevant in various fields such as mathematics, physics, engineering, and other scientific areas. It is commonly encountered in calculus courses as a challenging problem that requires the application of different integration techniques.

Understanding how to solve this integral is important for mastering these mathematical techniques and applying them to real-world problems in fields such as physics, engineering, and applied mathematics. It requires a solid understanding of trigonometry, calculus, and various integration methods such as integration by parts, trigonometric substitution, or reduction formulas.