Calculate the area of an isosceles triangle, the side and base of which are 15 cm and 18 cm, respectively.

To solve this problem, let us touch on the Pythagorean theorem: the square of the hypotenuse is equal to the sum of the squares of its legs.

This means that we need to know the length of the leg and the hypotenuse, so that we can then square them. We do it as follows:

We are looking for a leg: 18/2 = 9 (We divide the base into two parts, since the triangle is isosceles).

Then, according to the theorem, we are looking for the second leg, with the help of which we later find the area (S = 1/2 * bh, where b is the base of the triangle, and h is the height).

15 ^ 2 – 9 ^ 2 = 225 – 81 = 144 (12 from under the square).

S = 1/2 * 12 * 18 = 108.