# How do you use the Pythagorean Theorem to determine if the following three numbers could represent the measures of the sides of a right triangle: 20, 6, 21?

##### 2 Answers

The Pythagorean Theorem tells us that a triangle has a right angle if and only if the length of the longest side (the "hypotenuse") squared is equal to the some of the squares of the other two sides.

#### Explanation:

In this case, if the triangle were a right-angled triangle

Without doing the actual calculation we can see that

so these values can not be equal (and the triangle does not contain a right angle)>

Pythagorean Theorem refers to right-angled triangles.

#### Explanation:

In a right angled triangle, the square of the hypotenuse is equal to

the sum of the squares of the other two sides.

C will be the longest side of the triangle, in this case, 21

However,

Hence, it is not a right-angled triangle.