Prove that Cos 2A = CosA.SinA
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Answer:
cos2A=cosA-SinA
Step-by-step explanation:
let us start with LHS
cos2A can be expressed as
cos 2A=cos (A+A)
using the identity
cos (A+B)=cos(A).cos (B)
-sin (A).sin (B)
cos 2A= cosA . cosA- sinA .sinA
= cos2A - sin2A
=RHS
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