Pi day crossword puzzle

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Across
  1. 2. Only how many digits past the decimal point of pi are needed to accurately calculate the spherical volume of our entire universe
  2. 3. what Englishman calculated Pi to 707, but only 527 were correct
  3. 6. is a number (possibly a complex number) which is not algebraic—that is, it is not a root of a non-constant polynomial equation with rational coefficients
  4. 9. a straight line from the center to the circumference of a circle or sphere
  5. 10. pi day is celebrated in what month
  6. 11. is a name given to the ratio of the circumference of a circle to the diameter
  7. 12. The first theoretical calculation of a value of pi was calculated by him
  8. 16. is the distance around a two-dimensional shape
  9. 17. is the linear distance around the edge of a closed curve or circular object
  10. 18. carried out the longest calculation of pi to date on October 19, 2011
Down
  1. 1. the ancient who? generally calculated the area of a circle by taking 3 times the square of its radius
  2. 4. calculations of pi are used to test what?
  3. 5. is a real number that cannot be written as a simple fraction
  4. 6. pi is used in the branch of mathematics dealing with the relations of the sides and angles of triangles and with the relevant functions of any angles
  5. 7. infinite series of nested fractions
  6. 8. pi became popular after it was adopted by the Swiss mathematician...
  7. 13. who was the first to use the Greek letter pi to represent pi
  8. 14. a round plane figure whose boundary (the circumference) consists of points equidistant from a fixed point (the center)
  9. 15. pi is always... and does not change
  10. 19. the what? of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle