prove that 1/sec 2theta = cos^4 - sin ^4
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Step-by-step explanation:
LHS =cos
4
θ−sin
4
θ
=(cos
2
θ−sin
2
θ)(cos
2
θ+sin
2
θ)
=(cos
2
θ−sin
2
θ)(1)
=cos2θ
⇒ LHS = RHS
Hence proved
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