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: d=37. See explanation.

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:

d2=e2+f22efcosD

If we substitute the given values we get:

d2=82+3228334

d2=64+936

d2=7336=37

Answer:

D=37