# Resources tagged with: Proof by contradiction

### There are 3 results

Broad Topics >

Thinking Mathematically > Proof by contradiction

##### Age 11 to 14

This article for pupils and teachers looks at a number that even the great mathematician, Pythagoras, found terrifying.

##### Age 14 to 18

An introduction to proof by contradiction, a powerful method of mathematical proof.

##### Age 14 to 16

Challenge Level

We are given a regular icosahedron having three red vertices. Show
that it has a vertex that has at least two red neighbours.