Question

prove 1+cos2theta=2cos sqtheta​

Answer 1

Answer:

Step-by-step explanation:

cos(2∅)=cos²∅-sin²∅.

            =cos²∅-(1-cos²∅)       since cos²∅+sin²∅=1

             =2cos²∅-1.

adding 1 on left and right of '='.

1+cos2∅=cos²∅.