ECZ 2013 · O-Level Paper 1 — Circle Theorems

A circle centre O passes through the points A, B, C and D. Angle AOC = 110° and AO is parallel to BC. Find angle OCA.

Verified working — step 1

OA and OC are radii - triangle AOC is isosceles, and its base angles share what the 110° leaves.

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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