+37170 Area of a triangle = 1/2 b * h b = base h = height
base is 6.4 + 6.4 in this example
Find the height (the dotted line) using the Pythagorean theorem
6.4^2 + h^2 = 9^2
h^2 = 9^2 - 6.4^2
solve for 'h' then use the red equation above to find the area 
