Geometry crossword puzzle

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Across
  1. 2. a line segment that joins a vertex to the mid-point of the side that is opposite to that vertex
  2. 3. a polygon with 5 sides and 5 angles
  3. 7. opposite or contrary in position, direction, order, or effect.
  4. 9. an angle of exactly 90 degrees
  5. 12. a flat surface or area that extends infinitely in two dimensions and has no thickness
  6. 13. a point at or near the center or middle
  7. 15. a figure which is formed by two rays or lines that shares a common endpoint
  8. 16. the perpendicular drawn from the vertex of the triangle to the opposite side
  9. 17. the angles that lie opposite to each other when two lines intersect
  10. 19. a type of quadrilateral, whose opposite sides are equal and parallel
  11. 20. a line with a single endpoint (or point of origin) that extends infinitely in one direction
Down
  1. 1. a plane figure with four equal straight sides and four right angles
  2. 4. An angle smaller than the right angle
  3. 5. a statement that is assumed to be true based on basic geometric principles
  4. 6. a one-dimensional figure, which has length but no width
  5. 8. a line connecting the midpoints between two sides of a triangle
  6. 10. the total space taken up by a flat (2-D) surface or shape of an object
  7. 11. a location
  8. 14. the intersection point of all the three interior angle bisectors of the triangle
  9. 18. a general proposition not self-evident but proved by a chain of reasoning; a truth established by means of accepted truths.