Does the Pythagorean Theorem work on all triangles?

No, the pythagorean theorem only works on right triangles, but it will work on any right triangle.

This is because the Pythagorean Theorem states that length of Leg A squared plus the length of Leg B Squared equals the length of the hypotenuse squared. A hypotenuse is always found opposite a right angle. Only right triangles have right angles; therefore, the Pythagorean Theorem only applies to right triangles. :D