The perpendicular height is the height at a right angle to the base of the ... 𝒚. 𝒚 is half of 𝒙. Pythagoras’ theorem can then be used on either of the two right-angled triangles.

Circle theorems are properties that are true for ... at the centre is 180° and the angle on the circumference is half the angle in the centre, 90°. More simply, opposite angles in a cyclic ...