The math word puzzle

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Across
  1. 4. theorem A2+B2=C2
  2. 6. Add them all together
  3. 7. In the middle of a graph
  4. 8. It rotates at a specific angle and direction
  5. 9. It starts from zero
  6. 12. The one that you see the most
  7. 15. The difference of multiplication
  8. 16. It has negative and positive numbers
  9. 19. Wrapping something
  10. 20. The biggest one minus the smallest one
Down
  1. 1. The sides changes but it has the same distance and direction
  2. 2. (x,y)->(y,-x)
  3. 3. The difference of adding
  4. 5. (X,y)->(-x,-y)
  5. 10. The x and the y flips
  6. 11. The app we use the most
  7. 13. The side opposite of the right angle
  8. 14. d (X,y)->(-y,x)
  9. 17. The one in the
  10. 18. Doesn’t have congruence