Question

Can anyone proof this .......​

Answer 1

Here's your solution buddy

Answer 2

Step-by-step explanation:

Since ,

cos (A + B )=cosAcosB - sinAsinB

→Cos (A+A)= cos ^2A - sin ^2A

Since , Sin ^2 A = 1-cos ^2A .

and , Cos^2 = 1-sin^2A .

Thus ,

Cos2A = cos^2 -(1-cos^2A)=2cos^2A -1

Cos2A = (1-sin ^2A)-sin^2A =1-2sin^2A