The hypotenuse of a right triangle is the triangle's longest side; the side opposite the right angle. The length of the hypotenuse of a right triangle can be found using the Pythagorean theorem ...

The arrow and the word hypotenuse are coloured orange. The triangle is coloured pink., When using trigonometry in right-angled triangles, each side is labelled based on a given angle, Ɵ.

Learn how to find the angles in right-angled triangles with this BBC Bitesize Maths article. For students between the ages of 11 and 14.

MOST READERS will have encountered Pythagoras’s theorem about right-angled triangles—that the square on the hypotenuse is equal to the sum of the squares on the other two sides—at school.