pls see the attactment
Since and are tangent to the circle, then extending the radius to the point of tangency will form right angles with them, i.e.
Now, looking at , we know it is isosceles since . This implies . Using the fact that the angles of a triangle add up to , you can deduce that
So we have all the required angles to find and . To find , use the sine law for . Then to find , use the sine law again for (you'll need first).