**Triangle ﹣ Right Triangle**

A right triangle is a special type of triangle compared to general triangles because, as the name suggests, it has a right angle or a 90-degree angle. In the following section, we will use examples to calculate all the important values of the right triangle using the special formulas and calculation rules for right triangles.

On the page of our Triangle Calculator you will find a lot of information on calculating not only right triangles but also general triangles. Alternatively, visit our guides on the topics 'Area of a Triangle' and 'Equilateral Triangles'.

## Contents on the topic 'Right Triangle'

## Contents

### What are cathets?

In a right-angled triangle, the two sides that enclose the right angle are called the cathetes. Since the right angle in the illustration is at corner C, i.e., γ, the catheti are the two sides a and b that enclose it.

### What are the adjacent and opposite catheti?

Depending on the angle under consideration, the two catheti are also called the adjacent and opposite catheti. If we look at the non-right angle α at corner A in the illustration, side b is the adjacent cathetus to a (lies **at** the angle α to be examined ). The second cathetus a, which lies **opposite** the angle α, is the opposite cathetus to a. If, on the other hand, we look at the second non-rectangular angle β at corner B, the more precise designation of the two catheti is reversed: the adjacent catheti to β is a and the opposite catheti to β is the opposite catheti b.

### What is the hypotenuse?

While the cathetus are the two enclosing sides of the right angle in a right triangle, the hypotenuse is the side opposite the right angle. If the right angle is at point C, as shown in the illustration, the opposite side c is the hypotenuse. Since the right angle is always the largest angle in a right triangle, the hypotenuse is also always the longest side in a right triangle.

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## Source information

As source for the information in the 'Triangle' category, we have used in particular:

## Last update on February 20, 2023

The pages of the 'Triangle' category were last editorially reviewed by Michael Mühl on February 20, 2023. They all correspond to the current status.

### Previous changes on November 12, 2022

- 12.11.2022: Publication of an article Calculation of equilateral triangles.
- 12.11.2022: Publication of an article about Area of a triangle and about Right-angled triangles.
- 12.11.2022: Publication of the topic Calculate Triangle together with the corresponding texts.
- Editorial revision of all texts in this category