Izens puzzle

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Across
  1. 3. distance of a circle
  2. 8. adding and subtracting
  3. 9. not exact
  4. 10. the product of a number
Down
  1. 1. object with eight sides
  2. 2. measurements and angles
  3. 4. an approximate answer
  4. 5. forms a right angle
  5. 6. distance around a polygon
  6. 7. lines that never cross