First we have to see which is the right angle. This triangle has its legs oriented parallel to the axes. (-3,-1) and (1,-1) form the horizontal leg, (1,-1) and (1,2) the vertical leg.
So the right angle vertex is (1,-1) and the hypotenuse endpoints are (-3,-1) and (1,2)
The length is given by
[tex]d = \sqrt{ (1 - -3)^2 + (2 - -1)^2} = \sqrt{4^2+3^2}=\sqrt{25} = 5[/tex]
This is a 3/4/5 right triangle.
Answer: 5
