Math, asked by SudarshanPol, 7 months ago

prove the following-
COS
(x+y).cos (x-y) = cos^y – sin^x

Answers

Answered by SH0BHA

3

Step-by-step explanation:

LHS = cos(x+y).cos(x-y)

= (cosx.cosy - sinx.siny).(cosx.cosy + sinx.siny)

= cos²x.cos²y - sin²x.sin²y

= (1-sin²x).cos²y - sin²x.(1-cos²y)

= cos²y - sin²x.cos²y - sin²x + sin²x.cos²y

= cos²y - sin²x

= RHS

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