Given #A (-13, 2), B (5,17), C(22, -4)#
#a = sqrt((22-5)^2 + (-4-17)^2) = 27.0185#
#b = sqrt((22+13)^2 + (-4-2)^2) = 35.5106#
#c = sqrt((5+13)^2 + (17-2)^2) = 23.4307#
Semiperimeter #s = (a + b + c) / 2 = (27.0185 + 35.5106 + 23.4307 ) / 2#
#color(blue)(42.9799)#
Area of triangle
#A_t = sqrt ( s ( s-a) ( s-b) (s-c))#
#A_t = sqrt(42.9799 * (42.9799-27.0185) * (42.9799 - 35.5106) * (42.9799-23.4377))#
#A_t = sqrt(42.9799 * 15.9614 * 7.4693 * 19.5492)#
#color(brown)(A_t = 316.4992)#