MYP Maths: Pythagoras' Theorem FAQs

Pythagoras' theorem states that in any right-angled triangle, the square of the hypotenuse equals the sum of the squares of the other two sides: a² + b² = c². In MYP Maths you'll use it to find missing side lengths, check whether a triangle is right-angled, and solve real-world distance problems.

Most schools introduce Pythagoras' theorem in MYP 3 as a first pass, then build on it properly in MYP 4-5 with harder applications — 3D shapes, coordinate geometry, and mixed problems combining it with trigonometry. Exact timing depends on your school's curriculum map, since the IB doesn't fix a single year for each topic.

To find the hypotenuse, square both of the shorter sides, add the results together, then take the square root of that sum. For a right-angled triangle with legs 6 cm and 8 cm: 6² + 8² = 36 + 64 = 100, so the hypotenuse = √100 = 10 cm.

Yes — you apply it twice. First find the diagonal of a face using the two-dimensional formula, then use that diagonal as one side in a second right-angled triangle with the height to find the space diagonal running through the solid. This is common in MYP 4-5 problems on cuboids and prisms.

The mistake I see most often after years of marking: students add the two shorter sides squared but forget the hypotenuse is always the longest side and always opposite the right angle. Mislabel that, and every step after is wrong — check which side is 'c' before you touch a calculator.

Use Pythagoras' theorem when you know two sides of a right-angled triangle and need the third — no angles required. Switch to trigonometry (sine, cosine, tangent) when you're given one side and one angle, or need to find an angle itself. If a right angle isn't marked, check first before assuming either applies.

The converse states that if a² + b² = c² holds for the three sides of a triangle, the triangle must be right-angled — useful for proving a shape is right-angled rather than assuming it. MYP tasks often frame this as a real-world verification problem, like checking a foundation is square.

Pythagoras' theorem is assessed across MYP Mathematics' four criteria rather than as a stand-alone topic: Criterion A tests calculating missing sides correctly, Criterion B might ask you to investigate patterns in Pythagorean triples, Criterion C marks how clearly you show working and diagrams, and Criterion D applies it to real-life contexts like navigation or distances.

It can appear under any of the four MYP Mathematics criteria depending on the task: Criterion A (Knowing and understanding) for direct calculation, Criterion B (Investigating patterns) for exploring Pythagorean triples, Criterion C (Communicating) for clear mathematical reasoning, and Criterion D (Applying mathematics in real-life contexts) for word problems.

Both — many MYP schools set non-calculator tasks first to check you understand square roots and can simplify surds like √50 = 5√2, then allow calculators for multi-step or applied problems. Check your own school's assessment policy, since the IB sets criteria, not calculator rules, for internal MYP tasks.

Yes — both DP Mathematics: Analysis and Approaches and Mathematics: Applications and Interpretation assume Pythagoras' theorem as prior knowledge and build on it immediately, especially in trigonometry, vectors, and 3D geometry. According to the IB, first exams for the current Mathematics guides were 2021, and neither SL nor HL re-teaches it from scratch.

The theorem itself is identical, but MYP frames it through the four assessment criteria and real-world global contexts rather than exam-style grade descriptors. Your child's MYP 4-5 tasks may look less like a past-paper question and more like an investigation report — the maths is the same, the assessment structure differs.

Look for resources that mix short concept notes with plenty of practice: worked examples for 2D and 3D problems, mixed questions combining Pythagoras' theorem with trigonometry, and criterion-style tasks that mirror how MYP actually assesses it. On revisionprep.com you'll find MYP Mathematics Revision Notes and Topical Worksheets built around exactly this structure.