There are two theorems:
- All three angles AC_1B, AC_2B, AC_3B are equal. In general: All angles above a chord are equal.
- The size of any angle above a chord AB is half the size of angle AOB where O is the center of the circle.
I am Czech. In my native language there is a name of both these two statements separately.
- věta o obvodovém úhlu
- věta o středovém úhlu
What are these two theorems called in English?