A two dimensional shapes made from straight lines is called a polygon. A polygon has three or more sides.
When all the lines are the same length, and all the angles are the same, then the shape is a regular polygon.
A polygon has interior angles of 140º, 20º, 190º and 10º. Is it a regular polygon?
For a regular polygon, all angles have to be the same size.
Is it possible to have a regular polygon with only three sides?
An equilateral triangle has three sides, each of which are the same length. All the angles have the same value, 60º.
Answer: Yes - a triangle