Math 2.0

Sequences, series, summability Series: basic notions Theorem

Basel problem

Builds on p-series testpi

Statement

The series ∑n=1∞1n2\sum_{n=1}^{\infty} \frac{1}{n^2} converges, and ∑n=1∞1n2=1+14+19+⋯=π26.\sum_{n=1}^{\infty} \frac{1}{n^2} = 1 + \frac{1}{4} + \frac{1}{9} + \cdots = \frac{\pi^2}{6}.

Remarks

The convergence follows from the p-series test with p=2p = 2. The value is the hard part. The value π2/6≈1.6449\pi^2/6 \approx 1.6449 is ζ(2)\zeta(2), where ζ\zeta is the Riemann zeta function. Mathlib states it as hasSum_zeta_two.

History

Pietro Mengoli posed the problem in 1650. Leonhard Euler solved it in 1734. The problem is named after Basel, the home town of Euler.

Reading path

To understand this page from the ground up, read these 64 pages in order. The foundations come first.

  1. Harmonic number definition
  2. Limit point of a set definition
  3. Local maximum definition
  4. Sequence definition
  5. Limit of a function definition
  6. Local minimum definition
  7. Real sequence definition
  8. Subsequence definition
  9. Continuity at a point definition
  10. Derivative definition
  11. Bounded sequence definition
  12. Cauchy sequence definition
  13. Geometric sequence definition
  14. Limit of a sequence definition
  15. Monotone sequence definition
  16. Sequence tending to infinity definition
  17. Series definition
  18. Continuous function definition
  19. Fermat's theorem on stationary points statement
  20. Limit superior definition
  21. Cauchy sequences are bounded statement
  22. Sum of a finite geometric series statement
  23. Monotone convergence theorem for sequences statement
  24. Every sequence has a monotone subsequence statement
  25. Convergent sequence definition
  26. Pointwise convergence definition
  27. Squeeze theorem statement
  28. Partial sum definition
  29. Power series definition
  30. Intermediate value theorem statement
  31. Bolzano–Weierstrass theorem statement
  32. The sequence r^n tends to zero for |r| < 1 example
  33. Radius of convergence definition
  34. Uniform convergence definition
  35. Convergent series definition
  36. Sine and cosine definition
  37. Boundedness theorem statement
  38. Cauchy criterion for sequences statement
  39. Uniform convergence on a set definition
  40. Divergent series definition
  41. Absolute convergence definition
  42. A series of nonnegative terms converges iff its partial sums are bounded statement
  43. Series of functions definition
  44. Sum of a series definition
  45. Extreme value theorem statement
  46. Uniformly Cauchy sequence of functions definition
  47. Geometric series example
  48. Comparison test statement
  49. Cauchy condensation test statement
  50. Harmonic series example
  51. Rolle's theorem statement
  52. Root test statement
  53. Weierstrass M-test statement
  54. Harmonic series diverges statement
  55. Mean value theorem statement
  56. Cauchy–Hadamard theorem statement
  57. p-series test statement
  58. Power series converge uniformly on smaller discs inside the radius of convergence statement
  59. Uniform convergence of derivatives allows term-by-term differentiation statement
  60. Term-by-term differentiation statement
  61. Power series are differentiable inside the radius of convergence statement
  62. Derivative of cosine statement
  63. pi object
  64. Basel problem statement

Where this leads

1 page builds on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Basel_problem, lead section
About this page
Tag0DMY75D6FV
URIm2://0DMY75D6FV
Aliasessum-of-reciprocals-of-squares
Kindstatement, theorem
WritingW1 stated
MSC40A05
StatusThis copy of the site has no build data. Run m2 status 0DMY75D6FV.
Usesp-series test, pi
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