Trigonometry Examples

$\cos (- θ) = \cos (θ)$

Step 1

Start on the left side.

$\cos (- θ)$

Step 2

Since $\cos (- θ)$ is an even function, rewrite $\cos (- θ)$ as $\cos (θ)$ .

$\cos (θ)$

Step 3

Because the two sides have been shown to be equivalent, the equation is an identity.

$\cos (- θ) = \cos (θ)$ is an identity