Question 351559
{{{y= ((r-1)/(r+1))^1/2}}}
{{{y^2= (r-1)/(r+1)}}}
{{{y^2(r+1)= r-1}}}
{{{y^2r+y^2=r-1}}}
{{{r-y^2r=1+y^2}}}
{{{r(1-y^2)=1+y^2)}}}
{{{highlight(r=(1+y^2)/(1-y^2))}}}