Teach Genie
Teach it back in your own words, spot gaps, and remember it better.
Circle theorem questions are really about spotting structure in a diagram. Look for radii, chords, tangents, and shapes with all vertices on the circle.
The main angle facts come from three clues: equal radii, a tangent touching the circle, and angles standing on the same chord or arc. Start by marking these clues on the diagram before you calculate anything.
Question 1
4 marksPoints PPP, Q Q\,Q and R R\,R lie on the circumference of a circle with centre OOO. SRT SRT\,SRT is a tangent to the circle at point RRR.
PQ=QRPQ = QRPQ=QR Angle QRT=54∘QRT = 54^\circQRT=54∘
A [ ] is a straight line joining two points on the circumference.
Revision notes for WJEC GCSE Maths Circle Theorems: explanations and worked examples.
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Points AAA, BBB and CCC lie on a circle. A tangent touches the circle at CCC. Given that angle ABC=64∘ABC=64^\circABC=64∘ and angle ACB=73∘ACB=73^\circACB=73∘, find the angle between the tangent and chord CBCBCB.