# An Isosceles Mystery

- Author:
- John Golden

- Topic:
- Angles

David Marain (http://mathnotations.blogspot.com/, @dmarain) shared an angle chasing puzzle in the 80-80-20 isosceles triangle. Quite a nice one.
I chased a bit, then modeled in GeoGebra. Then I made a tool for making an ASA triangle which was handy for making angle chasing problems. Then I generalized the problem, and found that the 80-80-20 triangle had lots of neat situations that other triangles do not.
Is there something that makes this triangle special?
Tumblr post with several examples: http://mathhombre.tumblr.com/post/92497963079/david-marain-dmarain-shared-an-angle-chasing