Use the distance formula to find the length of each side.
AB = √((5+1)^2 + (-1-1)^2) = √(6^2+-2^2) = √40 = 2√10 = 6.3
BC = √((0+1)^2 +(-3-1)^2) = √(1^2 + -4^2) = √17 = 4.1
AC = √((0-5)^2 +(-3+1)^2) = √(5^2 + -2^2) = √29 = 5.4
Perimeter = 6.3 + 4.1 + 5.4 = 15.8
