Question

plz anyone help me to understand this

Answer 1

Heya User,

Recall the formula :->

--> sin²θ + cos²θ = 1 
--> cos 2θ = cos²θ - sin²θ = 2cos²θ - 1 = 1 - 2sin²θ

Now, in the second step -->
--> ( 1 + cos 2θ ) = 1 + 2cos²θ - 1 = 2 cos²θ
--> ( 1 - cos 2θ ) = 1 - ( 1 - 2sin²θ ) = 1 - 1 + 2 sin² θ = 2sin²θ

And so, after replacing the values, we get the second step ... :p