Some Circle Theorems

Image 0

The angle at the centre is twice the angle at the circumference for angles which stand on the same arc.

Image 1

Image 2

Angles at the circumference which are in the same segment are all equal.

Image 3

Image 5

An angle at the circumference which stands on the diameter of the circle is always a right-angle.

Image 4

Opposite angles of a cyclic quadrilateral add up to 180° (d+f = e+g = 180).

A tangent meets the radius of a circle at 90°.

The angle at the centre is twice the angle at the circumference for angles which stand on the same arc.	Image 1
	Image 2
Angles at the circumference which are in the same segment are all equal.	Image 3
	Image 5
An angle at the circumference which stands on the diameter of the circle is always a right-angle.	Image 4


Opposite angles of a cyclic quadrilateral add up to 180° (d+f = e+g = 180).

A tangent meets the radius of a circle at 90°.