The Pythagorean theorem is used specifically with right-angled triangles to find the length of one side when the lengths of the other two sides are known. It relates the squares of the two shorter sides (legs) to the square of the longest side (hypotenuse) using the formula a2+b2=c2a^2+b^2=c^2a2+b2=c2. This theorem can be applied to:

• Calculate the hypotenuse if the two legs are known.
• Find a missing leg when the hypotenuse and one leg are known.
• Solve various practical problems involving right triangles, such as distances and indirect measurements.

It is only applicable in the context of right triangles where one angle is exactly 90 degrees.