Solve the Blue Angle in a Simple Geometry Problem

[Apexny]

Homework Statement

http://i49.tinypic.com/2hyexk2.jpg

Find the blue angle. My apologies that the picture is not drawn to scale (some angles are misrepresented by the picture).

In case you have difficulties reading the picture, the angles are from the top, clockwise:

20, 10, 70, 60, 20

The attempt at a solution

http://i45.tinypic.com/jh39qa.jpg

These are all the angles labeled that can be easily proved. That's as far as my knowledge goes.

 

[ehild]

Have you learned the sine and cosine laws? Try to apply. It also might help that you have an other isosceles triangle, with 20o angles.

ehild