# How do I verify the following? #cos(x+y)cos(x-y)=cos^2x-sin^2y#

##### 2 Answers

#### Answer

#### Answer:

#### Explanation

#### Explanation:

Hello,

Use usual formulas :

So,

it means

But you know that

Develop and find

Simplify :

#### Answer

#### Answer:

#### Explanation

#### Explanation:

Describe your changes (optional) 200

Hello,

Use usual formulas :

So,

it means

But you know that

Develop and find

Simplify :

Describe your changes (optional) 200