Question

show that cos4theta +sin4theta =1-3 cos^2 theta sin^2 theta​

Answer 1

$\huge\purple{\mathfrak{answer:-}}$

LHS = cos ^4theta - sin ^4theta = (cos ^2theta - sin^2theta ) (cos ^2theta + sin ^2theta ) = (cos ^2theta - sin^2theta )(1) = cos 2theta LHS = RHS Hence proved

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