Help solving a precalculus problem for my son

[Proclivitas]

Homework Statement

Homework Equations

The Attempt at a Solution

This isn't for me, my son asked me to solve this, and I don't remember high school math, seeing that it isn't my field of study.

 

[scurty]

Can you reupload the image to a free image hosting site (http://imgur.com/, imageshack.us, etc)? I can't view that image as I'm not a member of Math Help Forum.

 

[Proclivitas]

Can you reupload the image to a free image hosting site (http://imgur.com/, imageshack.us, etc)? I can't view that image as I'm not a member of Math Help Forum.

 

[HallsofIvy]

Use the theorem that states that the measure of an angle, having vertex on the circumference of a circle, is half the measure of the arc subtended by the angle.