Topic explanation

Standard explanation

Already used to draw a circle through A,B,C. Radius R = OA. Acute triangles: O inside. Right: O is midpoint of the hypotenuse. Obtuse: O outside.

Key points

• vertices on the circle
• perp bisectors -> circumcentre
• angle bisectors -> incentre
• keep the ideas separate
• Circumcircle: Already used to draw a circle through A,B,C. Radius R = OA. Acute triangles: O inside. Right: O is m
• WHAT — CIRCUMCIRCLE: Already used to draw a circle through A,B,C. Radius R = OA. Acute triangles: O inside. Right: O is m
• 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: Already used to draw a circle through A,B,C. Radius R = OA. Acute triangles: O inside. Right: O is m

Labelled diagram