Question

let a=18°
show that Sin(2a)=cos(3a)

Answer 1

Answer:

Given a=18°

Sin 2a=Cos 3a

Sin (2×18)°= Cos (3×18)°

Sin 36°= Cos 54°

Sin (90-54)°= Cos 54°

Cos 54°= Cos 54°

Hence Proved.

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