Question

prove that cos(x+y) cos(x-y) =cos^x-sin^y​

Answer 1

Answer:

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Step-by-step explanation:

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Answer 2

Step-by-step explanation:

cos(x+y) cos(x-y)

(cosx•cosy-sinx•siny)(cosx•cosy+sinx•siny)

(a+b)(a-b)

a²-b²

so,

(cosx•cosy)²-(sinx•siny)²

cos²x•cos²y-sin²x•sin²y

cos²x•(1-sin²y)-(1-cos²x)sin²y

cos²x-cos²x•sin²y-sin²y+sin²y•cos²x

cos²x-sin²y-cos²x•sin²y+cos²x•sin²y

cos²x-sin²y

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