You would solve this as if it were a triangle. The distance between these 2 points is 2 in the x-value and 1 in the y-value. You use the Pythagorean theorem to find the rest, so 2^2+1^2=c^2 then becomes
4+1=c^2 which is then 5=c^2
c=about 2.236 units and that is the distance between the 2 points.
