Geometry Crossword Puzzle

2. Made up of seven points and angles. A 2D figure.
4. All the sides are treated equally, just like everyone should be. Meaning, they are all the same length.
5. A line segment connecting two points in a circle. A group of notes sounded together as a basis of harmony.
8. The "correct" triangle. It has a perpendicular angle in it.
10. A position in space that is infinitely small. A sharp tip, sometimes kinda moot.
12. A polygon with four sides. Also includes squares and stuff.
13. A straight line passing through the center of a circle. Reaches both sides of the circle.
15. 21 is a cool number. Happens to be the number of sides this polygon has.
16. Change, or difference. Also a wetland that forms as rivers empty their water into another body of water.
17. An ever-extending line originating from a singular point. An animal that swims in the ocean, a crestfallen kid in math class.
20. If you know this one, I would be subtly impressed. A shape with 900,000 sides.

1. Something assumed to be true. Used on the basis of reasoning or proof.
3. A 90 degree angle. Made by two intersecting lines.
6. A closed area that's pretty round. It also very fair to all it's points, making them each an equal distance from the center.
7. A branch of math pertaining to properties relating to points, shapes, and lines. Amongst other things.
9. All the angles are the same, just like identical triplets. Or quadruplets.
11. All sides are different and unique! Just like the humans that named this triangle.
14. A proposition that is not self evident. Proved by preexisting truths.
18. An infinitely long figure with no thickness. Twice as long as a Ray, even though he's already infinite in length.
19. Point of intersection of two sides of a shape on a 2D shape. Not to be confused with a mass of whirling fluid or air.