### Home > PC3 > Chapter 8 > Lesson 8.3.2 > Problem8-99

8-99.

Verify the following trigonometric identities.

1. $\cot^2\left(x\right)\left(\sec^2\left(x\right)-1\right)=1$

Substitute a Pythagorean Identity for $\sec^{2}\left(x\right) − 1$.

1. $\sin^2\left(α\right)-\cos^2\left(α\right)=1-2\cos^2\left(α\right)$

Substitute the Fundamental Pythagorean Identity into the left side of the equation for $\sin^{2}\left(α\right)$.