Topic explanation

Standard explanation

S is the semi-perimeter, not the perimeter. Missing the square root is a common error. r = Delta/S, so Delta = r S.

Key points

• S = a+b+c2
• (12)ab sin C
• Heron uses S
• keep the ideas separate
• Heron And R: S is the semi-perimeter, not the perimeter. Missing the square root is a common error. r = Delta/S,
• WHAT — HERON AND R: S is the semi-perimeter, not the perimeter. Missing the square root is a common error. r = Delta/S,
• 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: S is the semi-perimeter, not the perimeter. Missing the square root is a common error. r = Delta/S,

Labelled diagram