The Pythagorean theorem is a statement in geometry that shows the relationship between the side lengths of a right triangle - a triangle with an angle of -degrees. The right triangle equation is: Simply take the square root of both sides to find the length of your unknown side. 7 In our example, b, 16, taking the square root of, A right triangle has one angle. The Pythagorean Theorem In any right triangle, a2, b2, cc are the length of the hypotenuse and a and b are the lengths of the legs. Properties of rectangles. Rectangles have four sides and four 90° right angles. The lengths of opposite sides are equal.Classification of triangles using the Pythagorean theorem. We can use the Pythagorean theorem to determine whether a triangle is right, acute, or obtuse. To help you visualize this, think of an equilateral triangle with sides of . We know it is an acute triangle. If you plug each number into the file. So a is equal to the square root. I chose these numbers because they are both perfect squares. So this is equal to the square root times the square root,