MIDDLE SCHOOL


Hi Tammy, I expect that the teacher wants to emphasize that a mathematical definition is more precise than a description in common language. You might describe a circle as round or shaped like a dime, but a mathematical definition needs to be more precise and use terms that have been defined previously. For example a circle is defined as
The fixed point is called the center and the given distance the radius. For the others I would probably start with a polygon
Here "closed" means that the first and last points in the polygon coincide. A triangle is then a polygon with three sides and a hexagon is a polygon with six sides. I hope this helps, 

