You can put this solution on YOUR website! The key is that an "equilateral triangle" implies that ALL three sides are of equal lengths. Once you know that (if you draw a diagram), you can see that the "altitude" will bisect (divide it in half) one side of the triangle (at exactly 90 degrees). Now you can apply Pythagorean's theorem:
Let x = length of a side of the equilateral triangle
17.32^2 + (x/2)^2 = x^2
Solving for 'x' above will yield your answer.
