Mathematical cross words

1234567891011121314151617181920
Across
  1. 2. in which system there is no symbol for zero?
  2. 5. if 1=3,2=3,3=5,4=4 and 5=4 then 6=?
  3. 6. what is the other name of multiplication sign ?
  4. 8. who was the first person to make use of negative numbers
  5. 10. what is the mathematical recipe for working something out
  6. 11. what is the flat image that can be easily displayed in 3d called?
  7. 14. who constructed the first trigonometric table ?
  8. 16. if 13th March is Wednesday on 2024 then on 2028 what is the day?
  9. 17. what is the other name for international day of mathematics?
  10. 18. what comes before a quadrillion?
  11. 20. what may be mixed,complex or vulgar?
Down
  1. 1. what is XLII in Arabic numerals ?
  2. 3. what two digit number that is Twice the sum of their digits
  3. 4. name the polygon which has 15 sides ?
  4. 7. what does 1 followed by 100 zeros mean?
  5. 9. our measurement of time is based on which number system ?
  6. 12. apart from 1 which is the first positive number that is both as square and cube
  7. 13. two numbers whose product is 1 are called?
  8. 15. what maths term means as correct and exact as possible?
  9. 19. what was the symbol discovered by John Wallis