The Brainliest Answer!
take base 5 cm
and now take height as 5 cm at the both sides and now join the both sides now u will get the other side also as 5 cm

now it' s a square

hope this helped ...!!! @ :-)
2 5 2
1]draw base 5 cm
2] draw angles from both end points of 90 degrees 
3] from first end point mark an arc of 5 cm  same from other 
4] join the points of intersection of two arcs to the segments that is the 90 degrees lines .
see the figure for better understanding 
[from the figure ignore points f and g]