How do you prove sin^2 theta-cos^2 theta=2sin^2 theta-1?

Apr 13, 2016

Use the pythagorean identity ${\sin}^{2} \theta + {\cos}^{2} \theta = 1$.

Explanation:

Manipulating the identity, we get: ${\sin}^{2} \theta - 1 = - {\cos}^{2} \theta$

${\sin}^{2} \theta + {\sin}^{2} \theta - 1 =$

$2 {\sin}^{2} \theta - 1 = \to$ Identity proved

Hopefully this helps!