Geometry
posted by Ivan .
Compute the area of a triangle with sides.
15 × 15 × 18
a = How many square units?

There is a formula for the area of a triangle in terms of the side lengths.
Don't ask me to derive it. Here it is:
Let s = (a +b +c)/2
a,b and c are the side lengths.
For your triangle, s = 24
Area = sqrt[s*(sa)*(sb)*(sc)]
= sqrt[24*9*9*6) = 108 square units
Check: Your triangle is isosceles and if you drop a line from the apex to the middle of the base, you have two
9:12:15 right triangles. The area of each is (1/2)(9*12) and that makes a total area of 108.