Based on the given figure above, we can say that the measure of angle BDR is also 63°. R is meant to be tangent to the circle so, this makes the angle BDR equal to C. Angle C is half of the arc as well as BDR. Hope this is the answer that you are looking for.
It is given that line DR tangent to Circle O and m∠BCD=63°, then the measure of the angle BDR can be determined as:
Since, angle BDR is made between the chord and the tangent, and we know that the angle between a chord and a tangent through one of the end points of the chord is equal to the angle in the alternate segment, therefore
So in your circle their is a terminal point who is assigned by the value of P(x,y) and lies or determined by teh value of T=4pi/3. To get the coordinates of this terminal point first is to know what is the angle of the T and the answer is (-1/2, -sqrt(3)/2)
