### Home > A2C > Chapter 13 > Lesson 13.2.2 > Problem 13-118

13-118.

Prove that each of the following equations is an identity. In other words, prove that they are each true for all values for which the functions are defined. Homework Help ✎

sin^{2}θ + cos^{2}θ = 1

Recall the trigonometric ratios for sinθ, cosθ, and tanθ.

Substitute trigonometric ratios for tanθ and sec^{2}θ.

(sinθ)(sin^{2}θ + cos^{2}θ)

(sinθ)(1)

sinθ