How do you prove ## cos ^2theta - sin ^2 theta = 1 - 2sin^2 ...
How do you prove ## cos ^2theta - sin ^2 theta = 1 - 2sin^2 ...
The Pythagorean identity states that ##sin^2theta+cos^2theta=1##.
We can rearrange the identity to see that ##cos^2theta=1-sin^2theta##.
If we know that ##cos^2theta=1-sin^2theta##, we can replace ##c...
