Edexcel IGCSE Maths 复习笔记 4.6.4 Circle Theorems - Alternate Segment
What you need to know
- Alternate Segment Theorem
- The Alternate Segment Theorem states that the angle between a chord and a tangent is equal to the angle in the alternate segment
- You can spot this circle theorem by looking for a “cyclic triangle”
ie. all 3 vertices lie on the circumference) but one vertex lies on a tangent – look for where 2 chords meet a tangent
Questions often ask for “reasons” – aim to quote an angle fact or circle theorem for every angle you find, not just one for the final answer.