If both sides are 15, it is an isosceles triangle.
Half the triangle would be a right angle triangle.
Half the base would be (18 ÷ 2) = 9 cm
Find the height:
height² = 15² - (18 ÷ 2)²
height² = 144
height = √144
height = 12
area of triangle = 1/2 x 18 x 12 = 108 unit²
