Copy of Alternate segment theorem

On the screen, we see a circle with center A and also passing through B. A tangent is drawn at B and a chord BC is also drawn. Move the points A, B, C, D, E and F and observe how angles a, b, c and d change.
1. In every condition on comparing the values of a and c, what do you observe? 2. In every condition on comparing the values of b and d, what do you observe?