prove identity cos4asin4acos2aSolutioncos4asin4acos2a LHS co

prove identity cos^4a-sin^4a=cos(2a)

cos^4a-sin^4a=cos(2a)

LHS :cos^4a-sin^4a

(cos^2a +sin^2a)(cos^2a -sin^2a)

LHS : we know that :cos^2a +sin^2a =1

(cos^2a +sin^2a)(cos^2a -sin^2a) = 1*(cos^2a -sin^2a)

= (cos^2a -sin^2a)

= cos2a

RHS

prove identity cos^4a-sin^4a=cos(2a)Solutioncos^4a-sin^4a=cos(2a) LHS :cos^4a-sin^4a (cos^2a +sin^2a)(cos^2a -sin^2a) LHS : we know that :cos^2a +sin^2a =1 (cos

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