45-45-90 Triangle
How to find the sides of the given 45-45-90 triangle: definition, 2 examples, and their solutions.
Definition
Definition
A 45-45-90 triangle is a triangle
whose interior angles are 45º, 45º, and 90º.
The ratio of its sides is
1 : 1 : √2.
Its legs are congruent.
So a 45-45-90 triangle
is an isosceles right triangle.
Isosceles Triangle
Example 1
Example
Solution
The given interior angles of the triangle are
90º and 45º.
So this triangle is a 45-45-90 triangle.
So the top angle is 45º.
A 45-45-90 triangle is an isosceles right triangle.
So the blue sides are congruent.
So x is equal to the other side: 7.
So x = 7.
Example 2
Example
Solution
The given triangle is an isosceles right triangle.
So the given triangle is a 45-45-90 triangle.
So draw a 45-45-90 triangle
whose sides are 1, 1, and √2.
These two triangles are similar.
Then their sides are proportional.
So x/√2 = 11/1.
Similar Triangles
11/1 = 11
x/√2 = 11
Multiply √2 to both sides.
Then x = 11√2.
So x = 11√2.