Question

Cos^4(X)-Sin^4(X)=Cos^2(X)-Sin^2(X)​

Answer 1

Answer:

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Answer 2

Answer:

cos^4 x - sin^4x is in the form of a^4-b^4 =[a^2]^2-[b^2]^2=(a^2+b^2)(a^2-b^2)

=cos^4x-sin^4x=(cos^2x)^2-(sin^2x)^2=(cos^2+sin^2x) therefore we know that sin^2+cos^2= 1

since (1)(cos^2-sin^2)

=cos^2-sin^2

hence proved