ECZ 2017 · O-Level Paper 1 — Circle Theorems
In the diagram (A–F on a circle, angle FBD = 70°, angle AEF = 20°, AD a diameter), find angle DEF.
- A. 70°
- B. 90°
- C. 110°
- D. 160°
Verified working — step 1
Since AD is a diameter, angle AED = 90° (angle in a semicircle). Adding angle AEF = 20° gives angle DEF = 90° + 20° = …The full step-by-step working and final answer are included with Premium — checked against ECZ marking standards.
Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.
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