Right Angled Triangles

right angled scalene triangle

A right angled triangle is (you guessed it), a triangle that
has a right angle (90°) in it.

right angle symbol The little square in the corner tells us that 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).

Two Types

There are two types of right angled triangle:

right angled scalene triangle Scalene right angled triangle

One right angle
Two other unequal angles
No equal sides

 

Isosceles right angled triangle Isosceles right angled triangle

One right angle
Two other equal angles always of 45°
Two equal sides

 

 

Example: The 3,4,5 Triangle

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