In an early femoral triangle, the side is 15a base 18 and the cosine of the angle at base is three-fifths. Find the area of the triangle?

Let the base of the triangle be a = 18, and the sides are equal to b = 15 each. The height drawn from the top to the base will be denoted by the letter n. Determine the height n from a right-angled triangle, the legs of which are the height n and half the base – a / 2 = 18/2 = 9.

n ^ 2 = b ^ 2 – (a / 2) ^ 2 = 15 ^ 2 – 9 ^ 2 = 225 – 81 = 144.

Let’s determine the height n, since its square is equal to 144: n = 12.

The area of the triangle is:

s = (a * n) / 2 = 18 * 12/2 = 108 (square units).

In this problem, the value of the cosine of the angle at the base is a redundant data.