Question

Question #7cb3d

Answer 1

`2cos^2(x/2)=1+cosx`.

Explanation:

We use the following Result :

`2cosx*cosy=cos(x+y)+cos(x-y)`.

Now, `2cos^2(x/2)=2cos(x/2)cos(x/2)`,

`=cos(x/2+x/2)+cos(x/2-x/2)`,

`=cosx+cos0`.

`rArr 2cos^2(x/2)=1+cosx`.