All right triangles contain a 90-degree angle. This is the triangle's largest angle, and it is opposite to the longest side. If you have the distances of two sides or the distance of one side plus the measure of one of the right triangle's other angles, you can find the distance of all the sides. Depending on the information available, you can use either the Pythagorean theorem or trigonometric functions to find the length of any side. The study of right triangles finds applications in technical subjects like engineering, architecture and medicine.

Obtain the proper information to make the calculation. Sketch the right triangle and label the sides --- opposite, adjacent and hypotenuse --- in metric units. Insert the angles in degrees if the question contains that information, or use variable (theta) to label an unknown angle. Write the values for each side; ensure that they are in the same metric units.

Calculate one side when two sides are given. Calculate the length of a side (Y) using the Pythagorean theorem, which states that in a right triangle, the square of the hypotenuse is the sum of the squares of the other two sides. To calculate a length of hypotenuse, calculate adjacent length squared plus opposite length squared, and then calculate the square root of the result with the aid of a calculator.

To determine the opposite length, calculate hypotenuse length squared minus the adjacent length squared, and then calculate the square root of the result on a calculator. The calculation of adjacent length is similar to the method used to calculate opposite length. The metric unit of your calculated length is the same as those of the given lengths.

Calculate one side when a side and angle are given. Use the unknown-side label (Y), known-side label and known angle; identify the appropriate trigonometric function relating all three parameters. If the function is cosine, for example, and the unknown label is adjacent, calculate the cosine of the angle with a calculator to obtain a real number. Multiply the real number by the hypotenuse length. The result is the length of the adjacent side, and it has the same unit as the hypotenuse. The use of sine (opposite/hypotenuse) and tangent (opposite/adjacent) functions to find the distance of "Y" is similar to the method used with the cosine function.