Find the area of triangle ACE.
S = (7 + 8 + 9 ] / 2 = 12
Area =
sqrt [ S * (S - 7) (S - 8) (S - 9) ] =
sqrt [ 12 * 5 * 4 * 3 ] =
sqrt [ 12 * 12 * 5 ] =
12sqrt 5
