Question 851763
Polar coordinates might work better here. 
R is always the same, only theta changes.
{{{T[1]=tan^(-1)(y1/x1)}}}
{{{T[2]=tan^(-1)(y2/x2)}}}
{{{T[m]=(T[1]+T[2])/2}}}
{{{x[m]=R*cos(T[m])}}}
{{{y[m]=R*sin(T[m])}}}