For problem 8.26, isn't it A and B are very close to 0? Label the three points of the triangle P, Q, and R. Consider what happens when Q and R move towards the point P (and get very close to P), as shown below.

What happens to $\angle P$? What happens to the three areas A, B, and C?

For 8.28, the setup of the problem is identical to the example 8.8. That problem is done in the video lectures, I think around minute 38 has a diagram that can give a rough idea of the setup in 8.28. 

For 8.30, the drawing below (not necessarily to scale) can hopefully give a rough idea of the setup of the problem.

Remember that the line AD is tangent to the circle at A.

Hope these help!