Die Punkte sind A(0,5;1,5) und B(4;2) (Falls Du das gemeint hast...
s = sqrt{ (0,5-4)^2 +(1,5-2)^2 } = 5/2 *sqrt(2);
A(ax; ay) = A(0,5; 1,5); -> ax = 0,5; ay = 1,5;
B(bx; by) = B(4; 2); bx = 4; by = 2;
cx = bx -ax;
cy = by -ay;
c^2 = cx^2 +cy^2; | Pythagoras
c = sqrt{ cx^2 +cy^2 } = sqrt{ (bx -ax)^2 + (by -ay)^2 };