# Math Help - [SOLVED] trignometery law of cosines

1. ## [SOLVED] trignometery law of cosines

in triangle , p=5 cm, q=7cm and angle R=60 degrees. find r.

2. Hello, ramisha!

In triangle: $p=5$ cm, $q=7$ cm and $\angle R=60^o$ . Find $r.$

This is a straight-forward application of the Law of Cosines: . $r^2\;=\;p^2 + q^2 - 2pq\cos R$

We have: . $r^2 \:=\:5^2 + 7^2 - 2(5)(7)\cos60^o$

Can you finish it?