First we calculate lengths of each side of triangle.
AB = √((8-11)^2+(2-13)^2) = √130
BC = √(81+49) = √130
CA = √52
Since we have 2 equal lenghts and the lenght of third one is smaller than lenght of first 2 that means that triangle cannot be right and is in fact isosceles. Other way to test that to check for pythagoras theorem.
