basic math symbols

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Across
  1. 3. value (|x|)
  2. 6. root (√)
  3. 8. (+)
  4. 9. (-)
  5. 10. (×)
  6. 13. (π)
  7. 14. (÷)
  8. 16. (!)
  9. 18. than (>)
  10. 19. (∫)
  11. 20. (%)
Down
  1. 1. (⊥)
  2. 2. than or equal to (≤)
  3. 4. (∑)
  4. 5. (∞)
  5. 7. (=)
  6. 11. than (<)
  7. 12. (∥)
  8. 15. equal (≠)
  9. 17. than or equal to (≥)