# Derivative of cos square x

Learn what is the derivative of cos square x with formula. Also understand how to prove the derivative of cos^2x by different techniques.

Alan Walker-

Published on 2023-05-26

## Introduction to the Derivative of cos^2x

Derivatives have a wide range of applications in almost every field of engineering and science. The differentiation of cos square x can be calculated by following the rules of differentiation. Or, we can directly find the derivative of cos^2x by applying the first principle of differentiation.

In this article, you will learn what the derivative of cos^2x is and how to calculate the cos^2x derivative by using different approaches.

## What is the derivative of cos square x?

The cos square x derivative is equal to the negative of 2cos(x)sin(x) which is denoted as d/dx(cos^2x). It represents the rate of change of the trigonometric function cosine square.

Cosine, commonly denoted as cos, is a fundamental trigonometric function used to represent the ratio of the adjacent side of a right triangle to its hypotenuse. Thus, it can be written as;

cos(x) = adjacent side / hypotenuse

Knowing the derivative of cos squared x is essential in calculus and related fields, as it can help us find the slope of the curve at any given point.

## Derivative of cos2 x formula

The derivative of cos squared x can be calculated using the formula -2cos(x)sin(x), which represents the product of the sine and cosine functions. Mathematically, It is represented as;
d/dx(cos^2x)=-2cos xsin x
By using the chain rule and product rule, we can also find the derivative of cos3x. Knowing how to find the derivative of these trigonometric functions is important in calculus and related fields, as it can help us solve complex problems involving rate of change, slope, and optimization.

## How do you prove the differentiation of cos square x?

There are different ways to derive derivative of cos square x. Therefore, we can prove the derivative of cos2 x by using;

1. Chain Rule

2. Product rule

Each method provids a different way to compute the differentiation of cos square. By using these methods, we can mathematically prove the formula for finding derivative of cos square.

## Cos square differentiation by chain rule

To calculate the cos square differentation, we can use the chain rule since the cosine function can be expressed as a combination of two functions. The chain rule of derivatives states that the derivative of a composite function is equal to the derivative of the outer function multiplied by the derivative of the inner function. The chain rule of derivatives is defined as;

dy / dx = dy / du x du / dx

## Proof of cos^2x derivative by chain rule

To prove the derivative of cos squared by using chain rule, we start by assuming that,

y = u2 where u = cos x

By using chain rule calculator,

y = 2u. du/dx

And,

du/dx = -sin x

now, using the value of u and du/dx in y, we have,

y = - 2cos x.sin x

## Differentiation of cos square x by using product rule

The product rule is a formula used in calculus to calculate the derivative of the product of two functions. Specifically, the product rule is used when you need to differentiate two functions that are multiplied together. The formula for the product rule calculator is:

d/dx(uv) = u(dv/dx) + (du/dx)v

In this formula, u and v are functions of x, and du/dx and dv/dx are their respective derivatives with respect to x.

## Proof of cos square x differentiation by using product rule

To prove the cos^2x derivative by using product rule of derivative, we have,

d/dx (cos2x) = d/dx(cos x.cos x)

d/dx (cos2x) = cos x. (cos x) + cos x. (cos x)

d/dx (cos2x) = cos x.(- sin x)+ cos x.(- sin x)

It can be written as;

d/dx (cos2x) = - 2 sin x.cos x

Hence the cos square x derivative is proved by using product rule.

## How to find the derivative of cos 2x with a calculator?

The easiest way to calculate the derivative of cos square x is by using an online tool. You can use our derivative finder for this. Here, we provide you a step-by-step way to calculate derivatives by using this tool.

1. Write the function as cos^2x in the enter function box. In this step, you need to provide input value as a function as you have to calculate the differentiation of cos2x.

2. Now, select the variable by which you want to differentiate cos square x. Here you have to choose x.

3. Select how many times you want to differentiate cos^2x. In this step, you can choose 2 for second derivative, 3 for third derivative and so on.

4. Click on the calculate button.

After completing these steps, you will receive the cos square x derivative within seconds. Using online tools can make it much easier and faster to calculate derivatives, especially for complex functions.

### What are the 3 derivative rules?

The derivative rules are used to evaluate rate of change of a function easily. Some of derivative rules are;

1. Power Rule

2. Product Rule

3. Quotient Rule

### Why do we use 2nd derivative?

The second derivative of a function f can be used to determine the concavity of the graph of a function. A function whose second derivative is positive will be concave up. It means that the tangent line will lie below the graph of the function.

### Who is the father of derivatives?

It is very appropriate that the first history of derivatives should be written by the father-and-son team, Phelim and Feidhlim Boyle.