Property of a tangent

We can see a circle in black color with center A. There is a point B on the circumference of the circle. Two lines are drawn, ‘a’ is passing through both the points A and B and ‘b’ is passing through only point B while making an angle α with the first line. C is the point where line ‘b’ intersect the circle second time. We can change this angle α using the slide bar.
Questions to think about 1. What difference do we observe when angle α=90˚ and α≠90˚? 2. What do we observe when line ‘b’ cuts the circumference of the circle twice and when it just touches the circumference of the circle at one point?