Prove the following identity Dont send any links please - Maths - Introduction to Trigonometry

Question

Prove the following identity Dont send any links please

Brijendra Pal · Accepted Answer

Hi,
<img alt="" src=
"https://www%20nextgurukul%20in/media/images/q2aanswers/332/image002_1375351352467%20jpg">
= 221-cos2A-1= 21-2cos2A

Prove the following identity. Dont send any links please .