The height of an equilateral triangle is 30cm. find the exact area of the triangle. this is what i have done, am i on the right track?

The altitude turns an equilateral triangle into two 30 60 90 triangles.
The altitude is the side opposite the 60 degree angle.
In that case the hypotenuse (one of the 3 equilateral triangle sides) will equal altitude * 2 / sq root (3) = 30 * 2 / 1.7320508076
Equilateral triangle side = 34.6410161514
one half of the base = (1/2) * 34.6410161514 = 17.3205080757
The equilateral triangle area = (1/2) base * height
The equilateral triangle area = 17.3205080757 * 30 = 519.615
Source: http://www.1728.org/trig2.htm