A regular polygon has sides that are equal in length and equal angles. A regular triangle is called an equilateral triangle. A regular quadrilateral is called a square.

A regular polygon has sides that are equal in length and equal angles. A regular triangle is called an equilateral triangle. A regular quadrilateral is called a square.

Being two-dimensional, the inhabitants of Flatland appear as lines to one another. They discern one another's shape both by touching and by seeing how the lines appear to change in length as the ...