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Year 8 · Shapes & Geometry

Pythagoras: find the hypotenuse

In a right-angled triangle, the two short sides squared add up to the longest side squared: a² + b² = c².

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How to do it

  1. Square the two sides you know.
  2. Finding the hypotenuse: add, then square root.
  3. Finding a short side: subtract, then square root.

Worked example

Short sides 3 and 4
3² + 4² = 9 + 16 = 25
√25 = 5

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The hypotenuse is always opposite the right angle and always the longest.

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