Junior Cycle · Geometry
Lesson 11 of 12
JCHL Geometry 12: Proof of Theorem 19 (Practise)
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- You do NOT need to learn these proofs off for the new Junior Cycle — they are for understanding proofs
- Theorem 19: the angle at the CENTRE is twice the angle at the CIRCUMFERENCE standing on the same arc
- Construct a line through the centre, use the exterior-angle rule (Theorem 6) and isosceles base angles (equal radii)
- Finish the symmetric second half with the word "similarly"
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