It is important to know the theorems well and to learn to identify them in the diagrams. The angle subtended by an arc at the centre is twice the angle subtended at the circumference. More simply ...

When calculating angles using a circle theorem, always state which theorem applies. It may not be possible to calculate the missing angle immediately. It may be necessary to calculate another ...

They focused specifically on triangles whose angles were combinations of the original ... novel proofs of the Pythagorean ...