Hi. This question is on geometry with circle and triangle. But I am posting here and not in the Homework section because it is a problem that I am trying to do (so not Homework)... and because I am stuck only on 2 parts of the solution and not the whole solution... Thank you.... http://img256.imageshack.us/img256/9475/gtewp249no24.jpg [Broken] [ How did they get this? They never explained or proved this and it is NOT obvious from the picture. Blue: How is that implication true? By what theorem or reasoning?