Why can a rectangle also be a square?

Answer 1

it cant all sides have to be equilateral

edit- a rectangle cannot be a square. however, a square can be a rectangle.

reedit - A rectangle can be a square, however, a square must be a rectangle.

A rectangle has four 90 degree angles, which a square also has. The rectangle has two pairs of equal length sides, which a square also has. The only additional requirement for a square is that the length of all four sides be equal, which is not ruled out for a rectangle.