Solve a right triangle with the Pythagorean theorem — find the hypotenuse or a missing leg. Pick what to solve for and enter two sides.
Usage Tip
Common whole-number right triangles: 3-4-5, 5-12-13, 8-15-17. Multiples of these work too (6-8-10).
c is the hypotenuse, a and b are the legs
Rearranged, it finds a missing leg from the hypotenuse and the other leg.
Leg mode: enter the known leg, then the hypotenuse (which must be longer).
The result is a length, always positive.
The Pythagorean theorem says that in a right triangle the square of the hypotenuse equals the sum of the squares of the two legs. To find the hypotenuse, add the squared legs and take the square root. To find a missing leg, subtract the square of the known leg from the square of the hypotenuse and take the square root.
The hypotenuse is always the longest side and sits opposite the right angle, so when solving for a leg the hypotenuse you enter must be larger than the other side. Builders use the 3, 4, 5 triangle to check that a corner is square. The same theorem gives the diagonal of a rectangle and the distance between two points on a grid.