For any square the area is given by [tex]A=s^{2}[/tex] where [tex]s[/tex] is the length of one side. (This comes from the general rectangle formula [tex]A=lw[/tex] with [tex]l=w=s[/tex]).
To solve for [tex]s[/tex] we take the square root of both sides:
[tex]A=s^{2}[/tex]
[tex]\sqrt{A}=\sqrt{s^{2}}[/tex]
[tex]s=\sqrt{A}[/tex]
Now we can substitute known values:
[tex]s=\sqrt{A}[/tex]
[tex]s=\sqrt{479}[/tex]
[tex]s=21.886068 \approx 22feet[/tex]
