Lesson 5 Notes
A polygon is a close figure consisting of segments that intersect only at their endpoints. The endpoints are called vertices.
A convex polygon is a polygon in which any line segment connecting any two interior points of the polygon is in the interior of the polygon. If a polygon is not convex, it is concave.
For the rest of the unit, we will use the word "polygon" to mean "convex polygon."
A polygon with three sides is a triangle.
A polygon with four sides is a quadrilateral.
A polygon with five sides is a pentagon.
A polygon with six sides is a hexagon.
A polygon with seven sides is a heptagon.
A polygon with eight sides is a octagon.
A polygon with nine sides is a nonagon.
A polygon with ten sides is a decagon.
A polygon with twelve sides is a dodecagon.
Regular polygons are both equilateral and equiangular.
A parallelogram is a quadrilateral with two pairs of parallel sides.