The formula of a triangle is 1/2 base times the height of the triangle. for instance, if the top point of the triangle is at 3 on the graph, the right point of the triangle is at point 3, and the left point is at -3, the formula would be 1/2(6/the length of the base)(3/the height of the triangle at its highest point). therefore, 1/2(6)(3)= 9 units.