Easiest seems to be using the angles properties of a circle.
- angles on the same arc are equal,
- angle at the centre is twice the angle at the circumference,
- angle in a semi-circle is a right angle.
Call angle ABC $\displaystyle \theta,$ and using the third and first of these properties you should be able to fill in all of the other angles, (in terms of $\displaystyle \theta).$