Mathematics Puzzle

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Across
  1. 3. A function that can return the hyperbolic cosine of a number
  2. 5. The three dimensional analogue of a two dimensional circle
  3. 7. the unit of measuring liquid capacity
  4. 11. Sigma represents _______
  5. 12. Dividend = Divisor x ________ + Remainder
  6. 14. A polyhedron with 12 faces
  7. 15. A point where two or more lines/Curves/Edges meet
  8. 18. Determines the nature of the zeroes of a polynomial
  9. 19. The path followed by a flying projectile
  10. 20. A sequence having all real terms is called a _____ sequence
  11. 21. The state of oneness
Down
  1. 1. A closed curve bounded only by straight line segments
  2. 2. Pi was discovered by _____________
  3. 4. Euclid division lemma is applicable to all integers except this number
  4. 6. _________ progressions are used in many scientific and technical areas
  5. 8. The study of the relations of the sides and the angles of a triangle
  6. 9. A number which can be written without a fractional component
  7. 10. The number written above the line in a fraction
  8. 13. SI unit of measuring angles
  9. 16. The mathematical study of continuous change
  10. 17. __________ numbers form a series in which every number is the sum of its two preceding numbers