# Right-Angled Triangles

A |

The little square in the corner tells us it is a right angled triangle(I also put 90°, but you don't need to!) |

*The right angled triangle is one of the most useful shapes in all of mathematics!(It is used in the Pythagoras Theorem and Sine, Cosine and Tangent for example).*

Try it yourself (drag the points):

## Two Types

There are two types of right angled triangle:

Isosceles right-angled triangle

One right angle

Two other **equal** angles always of **45°**

Two equal sides

Scalene right-angled triangle

One right angle

Two other **unequal** angles

No equal sides

### Example: The 3,4,5 Triangle

The "3,4,5 Triangle" has a right angle in it.

(Draw one if you ever need a right angle!)

It has no equal sides so it is a **scalene** right-angled triangle

And, like all triangles, the three angles always add up to 180°.