Some Important Theorems of Circle

THEOREMS: 

1. The angle at the centre is twice the angle at the circumference.

2.The angle in a semi-cicle is 90°.

3. Angles in the same segment are equal.

4. Opposite angles in a cyclic quadrilateral add up to 180°.

5. The lengths of the two tangents from a point to a circle are equal.

6.The angle between a tangent and a radius in a circle is 90°.

7. Alternate segment theorem:

The angle (α) between the tangent and the chord at the point of         contact (D) is equal to the angle (β) in the alternate segment*.