Trigonometry Examples

$\sin (a) = \tan (a) \cdot \cos (a)$

Step 1

Start on the right side.

$\tan (a) \cdot \cos (a)$

Step 2

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

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

Step 3

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

$\sin (a)$

Step 4

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

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