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Resources tagged with Proof by contradiction similar to An Introduction to Irrational Numbers:

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Broad Topics > Using, Applying and Reasoning about Mathematics > Proof by contradiction

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An Introduction to Proof by Contradiction

Age 14 to 18

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

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The Dangerous Ratio

Age 11 to 14

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

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Proximity

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.