Question 368977
Use the distance formula,
{{{AB^2=(x[a]-x[b])^2+(y[a]-y[b])^2}}}
{{{AB^2=(a-2a)^2+(ab-2b)^2}}}
{{{AB^2=a^2+b^2(a-2)^2}}}
{{{highlight(AB=sqrt(a^2+b^2(a-2)^2))}}}