Pi

In a right triangle, the cathetus (plural, catheti) is either one of the two sides which, in a right triangle, are adjacent to the right angle. The remaining side, opposite the right angle, is called the hypotenuse. The cathetus is far more frequently known as a "leg" of the right triangle or, by the periphrasis "side about the right angle". When they are related to the hypotenuse, the catheti are often referred to simply as "the other two sides".

If a right triangle is not isosceles (i.e. it is scalene), then its catheti have different lengths and a distinction can be made between the "minor" one and the "major" one.

In Euclidean geometry, the lengths of the catheti are related to the length of the hypotenuse by the Pythagorean theorem.

Hypotenuse
.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, which states that the square of the length of the hypotenuse equals the sum of the squares of the lengths of the two other sides.

For example, if one of the other sides has a length of 3 metres (when squared, 9 m²) and the other has a length of 4 m (when squared, 16 m²). Their squares add up to 25 m². The length of the hypotenuse is the square root of this, or 5 m.