#"Incircle radius " r = A_t / s#
#A(4,5), B(3,2), C(1,3)#
#a = sqrt((3-1)^2 + (2-3)^2) = 2.236#
#b = sqrt((1-4)^2 + (3-5)^2) = 3.606#
#c = sqrt((4-3)^2 + (5-2)^2) = 3.162#
#"Semi-perimeter " s = (a + b + c) / 2 = (2.236 + 3.606 + 3.162) / 2 = 4,529#
#"A_t = sqrt(s (s-a) s-b) (s-c))#
#A_t = sqrt(4.529 (4.529-2.236) (4.529 - 3.606) (4.529 - 3.162)) = 3.62#
#color(cyan)("Radius of inscribed circle " r = A_t / s = 3.62/ 4.529 = 0.8 " units"#