Circle Proof

[Proclivitas]

Please solve.

 

[Proclivitas]

Is this homework?
Did you read "Read Before Posting"?

It is homework for my son, and being a 3D artist and not a mathematician, I don't remember highschool math.

 

[pappus]

View attachment 1847Please solve.

1. First go to this site: http://en.wikipedia.org/wiki/Inscribed_angle

2. Then have a look at the attached sketch. Use the marked triangle. The angles marked in yellow have the same size (value) Why?