I update my question because I missing the detail.
I include the lession example, for the small angle I can do no problem , but for big number I can solve
In circle C, point T is randomly selected so that it does not coincide with point P, segment SQ is a diameter of circle C.
1)Find the probability that m

Question

I update my question because I missing the detail.
I include the lession example, for the small angle I can do no problem , but for big number I can solve
In circle C, point T is randomly selected so that it does not coincide with point P, segment SQ is a diameter of circle C.
1)Find the probability that m <STQ = 90
2)Find the probability that m <PTQ = 180
the key for number 1 is : 1

The example lession is:
Point A and B are on cicrle so that art mAB=60 degree ,D is random located on the same circle that is not coincide with A or B. What is the probability of m<ADB=30degree?
arcmBDA=360- arcm