Mathematically Speaking

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Across
  1. 1. - subtract
  2. 5. Two lines sharing endpoints
  3. 7. 2 pi r
  4. 8. Square root symbol
  5. 10. not odd
  6. 11. Polygon with three sides
  7. 13. the same
  8. 15. not even
  9. 16. Part of the whole
Down
  1. 2. four equal sides
  2. 3. x times
  3. 4. Pi r squared
  4. 6. Each one hundred
  5. 9. ÷ find quotient
  6. 12. operator raising the power
  7. 14. + increase