Pythagoras theory finding short and long sides

Use Pythagoras' theorem to find a missing hypotenuse or a missing shorter side in a right-angled triangle.

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Learning objective overview

Master Teaching Guide coverage for this objective.

Current NZC (2007)
  • GM5-10
New NZC (2026)
  • NZC26-P4-MEA-MEA-P-Y9-06
  • NZC26-P4-MEA-MEA-P-Y9-07
  • NZC26-P4-MEA-MEA-P-Y10-10
  • NZC26-P4-MEA-MEA-K-Y9-08

Resources

  • CorbettMaths on using Pythagoras’ theory to find sidesQuestions PDF · Answers
  • Beta: Various from chapter 21

Terminology

  • Pythagoras' theorem
  • hypotenuse
  • short side
  • long side
  • right angle
  • right-angled triangle
  • square root

Task goals

  • Identify the hypotenuse as the longest side, opposite the right angle, before writing $a^2+b^2=c^2$.
  • Find a missing hypotenuse by adding the squares of the two shorter sides, then taking the square root.
  • Find a missing shorter side by subtracting a known square from the hypotenuse's square, then taking the square root.
  • Leave an answer as a simplified surd such as $\sqrt{19}$ when it is not a perfect square, unless asked to round.

Where this fits

What leads into this objective, and where it goes next.

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Pythagoras theory finding short and long sides

Pythagoras theory finding short and long sides

Do

Using Pythagoras' theorem to: verify that given side lengths in a right-angled triangle satisfy the theorem; find the length of the hypotenuse in a right-angled triangle, given the lengths of the other two sides

Statement▸
Year 9 · Measurement · Measuring
NZC26-P4-MEA-MEA-P-Y9-06
Do

Proving Pythagoras' theorem (e.g. by rearranging four congruent right-angled triangles into a square)

Statement▸
Year 9 · Measurement · Measuring
NZC26-P4-MEA-MEA-P-Y9-07

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