Topic explanation

Standard explanation

R=13, r=5: half-chord 12, chord 24. Same 5-12-13 triangle as chord-from-centre questions.

Key points

• Pythagoras again
• same centre
• outer chord tangent to inner
• keep the ideas separate
• Number: R=13, r=5: half-chord 12, chord 24. Same 5-12-13 triangle as chord-from-centre questions.
• WHAT — NUMBER: R=13, r=5: half-chord 12, chord 24. Same 5-12-13 triangle as chord-from-centre questions.
• HOW — Use the idea: Identify what is given, select this topic's rule or evidence, apply it one step at a time, and check
• CORE UNDERSTANDING: R=13, r=5: half-chord 12, chord 24. Same 5-12-13 triangle as chord-from-centre questions.

Labelled diagram