# In Triangle DEF, if e=8, f=3, and cosD=3/4, how do you find the exact value of d?

##### 1 Answer

Apr 29, 2017

Using the Law of Cosines we get:

#### Explanation:

The Law of Cosines lets you calculate the length of a side having two other sides and the value of cosine of the angle between them:

#d^2=e^2+f^2-2efcosD#

If we substitute the given values we get:

**Answer:**