cos 2x is one of the necessary trigonometric identities offered in trigonometry to uncover the value of the cosine trigonometric role for double angles. The is also called a dual angle identity of the cosine function. The identification of cos 2x helps in representing the cosine that a compound angle 2x in terms of sine and cosine trigonometric functions, in regards to cosine duty only, in terms of sine role only and in regards to tangent role only.

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cos 2x identity have the right to be acquired using various trigonometric identities. Allow us know the cos 2x identification in state of different trigonometric functions and also its derivation in information in the following sections.

 1 What is Cos 2x identification in Trigonometry? 2 Derivation that cos 2x using Angle enhancement Formula 3 Cos 2x In regards to sin x 4 Cos 2x In terms of cos x 5 Cos 2x In terms of tan x 6 Derivative and also Integral the cos 2x 7 How to use cos 2x Identity? 8 FAQs on cos 2x

## What is Cos 2x identity in Trigonometry?

Cos 2x is vital identity in trigonometry which can be express in various ways. It deserve to be expressed in terms of various trigonometric attributes such together sine, cosine, and tangent. Cos 2x is just one of the double angle trigonometric identities together the edge in factor to consider is a lot of of 2, the is, the dual of x. Let united state write the cos 2x identity in different forms:

cos 2x = cos2x - sin2xcos 2x = 2cos2x - 1cos 2x = 1 - 2sin2x ## Derivation that cos 2x making use of Angle enhancement Formula

We recognize that cos 2x can be expressed in four different forms. Us will use the angle addition formula for the cosine role to derive the cos 2x identity. Note that the edge 2x have the right to be written as 2x = x + x. Also, we know that cos (a + b) = cos a cos b - sin a sin b. Us will use this to prove the identification for cos 2x. Making use of the angle enhancement formula for cosine function, we have

cos 2x = cos (x + x)

= cos x cos x - sin x sin x

= cos2x - sin2x

Hence, we have cos 2x = cos2x - sin2x

## Cos 2x In terms of sin x

Now, that we have obtained cos 2x = cos2x - sin2x, we will certainly derive the formula because that cos 2x in terms of sine role only. Us will use the trigonometry identification cos2x + sin2x = 1 come prove the cos 2x = 1 - 2sin2x. We have,

cos 2x = cos2x - sin2x

= (1 - sin2x) - sin2x

= 1 - sin2x - sin2x

= 1 - 2sin2x

Hence , we have actually cos 2x = 1 - 2sin2x in terms of sin x.

## Cos 2x In terms of cos x

Just like we acquired cos 2x = 1 - 2sin2x, we will certainly derive cos 2x in regards to cos x, that is, cos 2x = 2cos2x - 1. Us will use the trigonometry identities cos 2x = cos2x - sin2x and cos2x + sin2x = 1 to prove the cos 2x = 2cos2x - 1. We have,

cos 2x = cos2x - sin2x

= cos2x - (1 - cos2x)

= cos2x - 1 + cos2x

= 2cos2x - 1

Hence , we have cos 2x = 2cos2x - 1

## Cos 2x In terms of tan x

Now, that us have derived cos 2x = cos2x - sin2x, we will derive cos 2x in regards to tan x. Us will use a few trigonometric identities and trigonometric formulas such as cos 2x = cos2x - sin2x, cos2x + sin2x = 1, and also tan x = sin x/ cos x. We have,

cos 2x = cos2x - sin2x

= (cos2x - sin2x)/1

= (cos2x - sin2x)/( cos2x + sin2x)

Divide the numerator and also denominator of (cos2x - sin2x)/( cos2x + sin2x) by cos2x.

(cos2x - sin2x)/(cos2x + sin2x) = (cos2x/cos2x - sin2x/cos2x)/( cos2x/cos2x + sin2x/cos2x)

= (1 - tan2x)/(1 + tan2x)

Hence, we have actually cos 2x = (1 - tan2x)/(1 + tan2x) in regards to tan x

## Derivative and also Integral that cos 2x

Derivative the cos 2x can quickly be calculated making use of the formula d/dx = -asin(ax + b). Similarly, integral that cos 2x can be easily obtained using the formula ∫cos(ax + b) dx = (1/a) sin(ax + b) + C. Therefore, we have actually d(cos 2x)/dx = -2sin 2x and ∫cos 2x dx = (1/2) sin 2x + C.

Hence the derivative that cos 2x is -2 sin 2x and the integral of cos 2x is (1/2) sin 2x + C.

## How to apply cos 2x Identity?

Cos 2x identity have the right to be used for solving different math problems. Let united state consider an instance to recognize the applications of cos 2x identity. We will recognize the worth of cos 120° utilizing the cos 2x identity. We recognize that cos 2x = cos2x - sin2x and also sin 60° = √3/2, cos 60° = 1/2. Due to the fact that 2x = 120°, x = 60°. Therefore, us have

cos 120° = cos260° - sin260°

= (1/2)2 - (√3/2)2

= 1/4 - 3/4

= -1/2

Important notes on cos 2x

cos 2x = cos2x - sin2xcos 2x = 2cos2x - 1cos 2x = 1 - 2sin2xcos 2x = (1 - tan2x)/(1 + tan2x)The derivative that cos 2x is -2 sin 2x and the integral of cos 2x is (1/2) sin 2x + C.

Related subject on cos 2x

## Examples utilizing cos 2x

Example 1: Prove the triple angle identification of cosine function using cos 2x formula.

Solution: The triple angle identity of the cosine role is cos 3x = 4 cos3x - 3 cos x

To start with, we will usage the angle enhancement formula the the cosine function.

cos 3x = cos (2x + x) = cos 2x cos x - sin 2x sin x

= (2cos2x - 1) cos x - 2 sin x cos x sin x

= 2 cos3x - cos x - 2 sin2x cos x

= 2 cos3x - cos x - 2 cos x (1 - cos2x)

= 2 cos3x - cos x - 2 cos x + 2 cos3x

= 4 cos3x - 3 cos x

Answer: Hence, we have proved cos 3x = 4 cos3x - 3 cos x using the cos 2x formula.

Example 2: Express the cos 2x formula in regards to cot x.

Solution: We understand that cos 2x = (1 - tan2x)/(1 + tan2x) and tan x = 1/cot x

cos 2x = (1 - tan2x)/(1 + tan2x)

= (1 - 1/cot2x)/(1 + 1/cot2x)

= (cot2x - 1)/(cot2x + 1)

Answer: Hence, cos 2x = (cot2x - 1)/(cot2x + 1) in terms of cotangent function.

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## Practice questions on cos 2x

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## FAQs ~ above cos 2x

### What is cos 2x identification in Trigonometry?

Cos 2x is among the twin angle trigonometric identities as the edge in factor to consider is a lot of of 2, the is, the double of x. It can be expressed in terms of different trigonometric attributes such as sine, cosine, and tangent.

### What is cos 2x Formula?

It deserve to be express in state of different trigonometric features such as sine, cosine, and tangent. It can be expressed as:

cos 2x = cos2x - sin2xcos 2x = 2cos2x - 1cos 2x = 1 - 2sin2x

### What is the Derivative of cos 2x?

The derivative that cos 2x is -2 sin 2x. Derivative that cos 2x can easilty it is in calculated utilizing the formula d/dx = -asin(ax + b)

### What is the Integral of cos 2x?

The integral that cos 2x have the right to be easilty acquired using the formula ∫cos(ax + b) dx = (1/a) sin(ax + b) + C. Therefore, we have actually ∫cos 2x dx = (1/2) sin 2x + C.

### What is cos 2x In regards to sin x?

We have actually cos 2x = 1 - 2sin2x in regards to sin x.

### What is cos 2x In terms of tan x?

We have actually cos 2x = (1 - tan2x)/(1 + tan2x) in regards to tan x.

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### How to have cos 2x Identity?

Cos 2x identity have the right to be acquired using various identities such together angle sum identification of cosine function, cos2x + sin2x = 1, tan x = sin x/ cos x, etc.