Circle Theorems Flashcards

The angle in a semicircle is always 90° (a right angle).

The angle at the centre of a circle is twice the angle at the circumference subtended by the same arc.

Angles in the same segment of a circle are equal.

The opposite angles of a cyclic quadrilateral add up to 180°.

A tangent to a circle is perpendicular to the radius at the point of contact.

Tangents drawn from an external point to a circle are equal in length.

The angle between a tangent and a chord through the point of contact is equal to the angle in the alternate segment.

The perpendicular from the centre of a circle to a chord bisects the chord.

The angle subtended by a diameter at the circumference is a right angle.

Chords of equal length are equidistant from the centre of the circle.