# How do you solve the #triangle RST# given #R=35^circ, s=16, t=9#?

##### 1 Answer

You're given the included angle. Use the Law of Cosines to solve this problem.

The formula :

Let's replace

Let's solve for side

Substitute values.

Now, let's solve for angle S.

You can solve using the Law of Sines, but I'll just use the Law of Cosines because you didn't seem to know how to do it.

Also, for the sake of simplicity, I'll just use

The rearranged formula of the Law of Cosines (and changed to our variables *r, s and t*) :

Substitute values :

You can work out the remaining angle using the angles in a triangle add up to 180 rule.