Precalculus Examples

$\tan (θ) \cdot \cos (θ) = \sin (θ)$

Step 1

Start on the left side.

$\tan (θ) \cdot \cos (θ)$

Step 2

Write $\tan (θ)$ in sines and cosines using the quotient identity.

$\frac{\sin (θ)}{\cos (θ)} \cdot \cos (θ)$

Step 3

Cancel the common factor of $\cos (θ)$ .

$\sin (θ)$

Step 4

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

$\tan (θ) \cdot \cos (θ) = \sin (θ)$ is an identity