The midpoint is calculated by averaging the coordinates of its endpoints:
[tex]M = \left(\dfrac{-2+8}{2},\dfrac{0+2}{2}\right)=(3,1)[/tex]
Now we can use the usual distance formula to get the length of SM:
[tex]SM=\sqrt{(2-3)^2+(8-1)^2}=\sqrt{1+49}=\sqrt{50}[/tex]
