Properties of Circles

For a circle, two tangents, PX and PY can be drawn from an external point P.

Tangent makes an angle of 90° with radius of the circle.

PX = PY

< XOP = < YOP and < XPO = < YPO

A four sided polygon whose vertices touch the circumference of a circle is called Cyclic Quadrilateral.

Sum of diagonally opposite angles of a cyclic quadrilateral is 180°.

<a + <b = 180°

<c + <d = 180°