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

In order to find the diagonal of a rectangle, if the sides of the rectangle are 9 cm and 12 cm, we will use the Pythagorean theorem.

Let’s consider a triangle formed by the sides of a square and a diagonal.

The triangle is rectangular, the adjacent sides of the rectangle are the legs, and the diagonal of the rectangle is the hypotenuse.

Let’s apply the Pythagorean theorem. The square of the hypotenuse is equal to the sum of the squares of the legs.

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

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

c ^ 2 = 81 + 144;

c ^ 2 = 225;

c = √225;

c = 15 cm.

Answer: 15 cm diagonal of the rectangle.