# How do you determine #costheta# given #tantheta=2/3, pi<theta<(3pi)/2#?

##### 1 Answer

Please see the explanation.

#### Explanation:

Start with the identity

Divide both sides by

Use the identity

Solve for

The domain restriction

Substitute

Dec 17, 2016

Please see the explanation.

Start with the identity

Divide both sides by

Use the identity

Solve for

The domain restriction

Substitute