Trigonometry Examples

$\sin (a + b) = \sin (a) \cos (b) + \cos (a) \sin (b)$

Step 1

Start on the left side.

$\sin (a + b)$

Step 2

Apply the sum of angles identity.

$\sin (a) \cos (b) + \cos (a) \sin (b)$

Step 3

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

$\sin (a + b) = \sin (a) \cos (b) + \cos (a) \sin (b)$ is an identity