# How do you use #tantheta=4# to find #costheta#?

##### 2 Answers

#### Explanation:

You could use the identity

Unfortunately the sign of

#### Explanation:

If

then the ratio of the opposite side to the adjacent side is

Two possibilities exist depending upon whether

In either case the relative length of the hypotenuse is given by the Pythagorean Theorem as

Since

for this case