hmmm ok... we know C and F, what is M anyway?
[tex]\bf ~~~~~~~~~~~~\textit{middle point of 2 points }\\\\
\begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&C&(~ 4 &,& 10~)
% (c,d)
&F&(~ 8 &,& 8~)
\end{array}\qquad
% coordinates of midpoint
\left(\cfrac{ x_2 + x_1}{2}\quad ,\quad \cfrac{ y_2 + y_1}{2} \right)
\\\\\\
\left( \cfrac{8+4}{2}~,~\cfrac{8+10}{2} \right)\implies \stackrel{M}{(6,9)}[/tex]
ok, what is the length of the segment MF then?
[tex]\bf ~~~~~~~~~~~~\textit{distance between 2 points}\\\\
\begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&M&(~ 6 &,& 9~)
% (c,d)
&F&(~ 8 &,& 8~)
\end{array}~~~
% distance value
d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2}
\\\\\\
MF=\sqrt{(8-6)^2+(8-9)^2}\\\\\\ MF=\sqrt{2^2+(-1)^2}\implies MF=\sqrt{5}[/tex]
