angles opposite to equal sides of triangle are equal

Angles of a triangle change when the length of its sides is changed. On the screen, you see a triangle ABC in red color. Observe how the angles of this triangle change when length of the sides AC (b) and BC (a) are changed using their respective slide bars.
Question/s to think about. 1. What is the relation between angles A and B when we set a=b using the slide bar?