Pythagoras and trigonometry
Lesson 4 of 14
Pythagoras' theorem
Objective. Find a missing side in a right-angled triangle.
The key idea
a² + b² = c², where c is always the hypotenuse — the side opposite the right angle.
Worked example
A right triangle has legs 5 cm and 12 cm. Find the hypotenuse.
- 15² + 12² = 25 + 144 = 169.
- 2√169 = 13.
Answer: 13 cm
Practice
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