r = s/p
s = radical p (p - a)(p - b)(p - c)
p = (a + b + c) : 2 = (14 + 16 + 18) : 2 = 48 :2 = 24
s = radical 24(24 -16)(24 -14)(24 - 18) = radical 24 x 8 x 10 x 6 =
= radical 11520 = radical 2304 x 5 = 48 radical 5
r = 48 radical 5 / 24 = 2 radical din 5