Right Triangles
A right triangle (also called right angled triangle) has a right angle (90°) in it.
 |
The little square in the corner tells us it is a right triangle (I also put 90°, but you don't need to!) |
The right triangle is one of the most useful shapes in all of mathematics!
It is used in the Pythagoras Theorem and Sine, Cosine and Tangent and more.
Try it yourself (drag the points):
geometry/images/triangle.js?mode=right
Two Types
There are two types of right triangle:
Isosceles right triangle
- One right angle
- Two other equal angles always of 45°
- Two equal sides
Scalene right 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 triangle
And, like all triangles, the three angles always add up to 180°.
Can a right triangle be equilateral?
No! An equilateral triangle has all three angles equal to 60°. Since a right triangle must have a 90° angle, it can't be equilateral.
6701, 6707, 761, 1800, 762, 1801, 3228, 3229, 8997, 8998