Find the diagonal of the rectangle if the sides are 9 and 12 cm.

From the condition, we know the lengths of the sides of the rectangle, they are 9 and 12 cm.In order to find the length of the diagonal of the rectangle, let’s consider a right triangle, which is formed by the sides of the rectangle (legs of the triangle) and the diagonal of the triangle (hypotenuse of the right triangle).

To find the hypotenuse of a triangle, we will use the Pythagorean theorem.

Which says that the sum of the squares of the legs is equal to the square of the hypotenuse.

a ^ 2 + b ^ 2 = c ^ 2;

c ^ 2 = 9 ^ 2 + 12 ^ 2;

c ^ 2 = 81 + 144;

c ^ 2 = 225;

c = 15 cm the length of the diagonal of the rectangle (hypotenuse).