MathematicsCode 4024
Circle theorems I
What this topic asks you to be able to do
- Work out unknown angles and give reasons, using these circle facts: angle in a semicircle = 90°; angle between a tangent and a radius = 90°; the angle at the centre is double that at the circumference; any two angles in the same segment of the circle are equal; a cyclic quadrilateral has opposite angles that total 180° (they are supplementary); and the alternate segment theorem.