Question 373250
{{{drawing(300,300,-10,10,-10,10,line(-4,4,4,4),line(4,4,4,-4),line(4,-4,-4,-4),line(-4,-4,-4,4),blue(line(4,4,-4,-4)),locate(0,0,sqrt(10)),locate(0,-4,s),locate(4.5,0,s))}}}
Use the Pythagorean theorem,
{{{s^2+s^2=(sqrt(10))^2}}}
{{{2s^2=10}}}
{{{s^2=5}}}
{{{highlight(s=sqrt(5))}}}