# Right Angled Triangles

### Overview

– Pythagoras’ theorem

– Trigonometry: the sine ratio

– Trigonometry: the cosine ratio

– Trigonometry: the tangent ratio

### Example Key Words

## Hypotenuse

The longest side of a triangle. It is also the side opposite the right angle.

## Pythagoras' Theorem

A theorem stating that in a right triangle the area of the square on the hypotenuse is equal to the sum of the areas of the squares drawn on the other two sides.

## Opposite and Adjacent Side Side

The side opposite (opposite) and next to (adjacent) the angle you are dealing with in a triangle (not the right angle)

## The Sine Ratio

The sine of an angle in a right triangle is defined as the ratio of the length of the side opposite the angle to that of the hypotenuse.

## The Cosine Ratio

The cosine of an angle in a right triangle is defined as the ratio of the length of the side adjacent to the angle to that of the hypotenuse.

## The Tangent Ratio

The tangent of an angle in a right triangle is defined as the ratio of the length of the side opposite the angle to that of the adjacent side.