Find, giving a reason3 marksIGCSE
A, B, C and D lie on a circle in that order. Angle ABC = 74°. Find angle ADC, giving a reason for your answer.
Show the mark scheme and the examiner note
Answer: 106°, because opposite angles of a cyclic quadrilateral add to 180°.
- ABCD is a cyclic quadrilateral
- Opposite angles sum to 180°
- 180 − 74 = 106°
Examiner technique: Circle theorem questions carry a reason mark. A correct number with no theorem named typically loses one third of the marks available.