Pythagorean Theorem Examples in Math

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Pythagorean Theorem.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Math.

Concept Recap

In a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides.

If you draw squares on each side of a right triangle, the two smaller squares fill the big one exactly.

Read the full concept explanation โ†’

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: A fundamental relationship between sides of right triangles.

Common stuck point: c must be the longest side (hypotenuse), opposite the right angle.

Sense of Study hint: Ask yourself: which side is across from the 90-degree angle? Label that one c, then plug the other two into a-squared plus b-squared.

Worked Examples

Example 1

easy
A right triangle has legs of length 3 and 4. Find the hypotenuse.

Solution

  1. 1
    Apply the Pythagorean theorem: a^2 + b^2 = c^2.
  2. 2
    Substitute: 3^2 + 4^2 = c^2 \Rightarrow 9 + 16 = c^2 \Rightarrow c^2 = 25.
  3. 3
    Take the positive square root: c = \sqrt{25} = 5.

Answer

c = 5
The Pythagorean theorem relates the three sides of a right triangle. The hypotenuse (opposite the right angle) is always the longest side. The 3-4-5 triple is the most common Pythagorean triple.

Example 2

medium
A right triangle has a hypotenuse of 13 and one leg of length 5. Find the other leg.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

hard
A ladder 10 m long leans against a wall. The foot of the ladder is 6 m from the base of the wall. How high up the wall does the ladder reach?

Example 2

hard
A right triangle has legs of length x + 1 and x + 8, and hypotenuse 13. Find x.

Background Knowledge

These ideas may be useful before you work through the harder examples.

trianglesexponentssquare roots