Question

Prove that (1+2sinx )(1-2sinx)(1+2cosx)=1+2cos4x

Answer 1

Step-by-step explanation:

SEE THE ATTACHED PICTURE

Answer 2

Answer:

$(1 + 2 \sin \alpha )(1 - 2 \sin \alpha )(1 + 2 \cos \alpha ) = 1 + 2 \cos4 \alpha \\ lhs = (1 + 2 \sin \alpha )(1 - 2 \sin \alpha )(1 + 2 \cos \alpha ) \\ = 1 - 4 \sin^{2} \alpha (1 + 2 \cos \alpha ) \\ = 4 \cos{}^{2} \alpha (1 + 2 \cos \alpha ) \\ =$

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