What is the formula to calculate the diagonal of a rectangle?

To determine the diagonal of a rectangle, the relevant geometric principle relies on the Pythagorean theorem, which is applied in right triangles. In the context of a rectangle, where 'a' and 'b' represent the lengths of the sides, the diagonal 'c' forms the hypotenuse of the right triangle created by the two sides.

Using the Pythagorean theorem, the formula states that the sum of the squares of the lengths of the two legs (the sides of the rectangle) is equal to the square of the length of the hypotenuse (the diagonal). This relationship can be expressed mathematically as a² + b² = c².

Therefore, this formula accurately reflects how to calculate the length of the diagonal based on the dimensions of the rectangle, affirming its correctness in this context. This essential geometric concept is foundational in mathematics and applies broadly in various fields, such as architecture and engineering.