Shape and Space 2
3 marks · NormalA, B, C, and D lie on a circle with centre O. Angle ABC is 115°.
(a)[2 marks]
Work out the size of angle CDA.
(b)[1 mark]
Explain why your answer is correct.
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(a) 65 degrees
(b) Opposite angles in a cyclic quadrilateral sum to 180°.
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · States or uses the property that opposite angles of a cyclic quadrilateral sum to 180°
A1 (a) · 1 mark · Calculates that angle CDA = 65°
B1 (b) · 1 mark · Explains the reason using the circle theorem for cyclic quadrilaterals.
Worked solution
Opposite angles in a cyclic quadrilateral add up to 180°.