1- Learn the Pythagorean theorem. The Pythagorean theorem describes the relationship between the sides of a right triangle. He states that for any triangle rectangle with sides of length a and b, and hypotenuse of length c, a2 + b2 = c2.
2- First: make sure it's even a rectangle triangle. The Pythagorean theorem only has an effect on triangle rectangles, and by definition, only rectangular triangles have a hypotenuse. If your triangle has an angle with exactly 90 degrees, it is a right triangle, and you can continue.
Straight angles are often noticed in textbooks and academic proofs with a small square at the corner of the angle. This special mark represents the indication "90 degrees".
3- Set the variables a, b, and c to the sides of the triangle. The variable "c" will always represent the hypotenuse, or the side of greater extension. Choose one of the other sides to be a and give the other the denomination b (the order is irrelevant because the result will be the same). Next, enter the lengths of a and b in the formula, according to the following example:
If your triangle has sides of lengths 3 and 4, and you have defined letters to these sides, such as a = 3 and b = 4, you can write the equation as follows: 32 + 42 = c2