## Algebra 2 Common Core

$$\sin\theta=\pm\sqrt {1-\cos^{2}\theta}$$
Start with the Pythagorean identity $$\cos^{2}\theta+\sin^{2}\theta=1.$$ Rearrange terms and solve for $\sin\theta$: $$\sin^{2}\theta=1-\cos^{2}\theta$$ $$\sin\theta=\pm\sqrt {1-\cos^{2}\theta}.$$