The Curious Engineer

All blogs / Math

johndcook.com

johndcook.com/blog

MathSoftware / engineering practice

’10’15’20’25
Posts
236 from 6 Apr 2009 to 3 Nov 2026
Posting
weekly (117 in the last year)
Kind
personal blog

2026 110

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  6. The Unbalanced Group Theorem
  7. The Exponential Time Hypothesis is False
  8. Where else to find me
  9. Inversion in an ellipse
  10. geometric construction
  11. Duality in spherical trigonometry
  12. Computing polar triangles with linear algebra
  13. this post
  14. How the eMudrha certificate debacle might have happened
  15. Working around a strange Python problem
  16. earlier post
  17. Deliberate imperfection
  18. A frivolous problem with a deeper lesson
  19. Refactoring factorials
  20. Cloud of suspicion lifted from NIST curves
  21. Monoliths and Lagrange Points
  22. Poe, Bessel, and Drones
  23. A generalization of the Pythagorean theorem
  24. LaTeX package for Pascal-like triangles
  25. harmonic triangle
  26. Categorical models of logics
  27. Privacy policies and modal logic
  28. Irrationality exponent of π
  29. Faster Fourier Transform
  30. Consequences of progress toward the Riemann Hypothesis
  31. A topological model for provability logic
  32. Lissajous and Bowditch
  33. Topological models of modal logic
  34. Miquel’s pentagon theorem
  35. previous post
  36. earlier post
  37. Servers in dawn-dusk orbit
  38. Navigation minimum
  39. Nathaniel bowditch
  40. Haversine law
  41. Why fitting a logistic is nearly impossible from early data
  42. Phone words
  43. Empirical fractal
  44. Converting between cosine similarity and concentration ratio
  45. Coffee milk latte
  46. Fibonacci product
  47. Cosine similarity
  48. Simple approximation for spherical cap area
  49. Guessing the meaning of a number
  50. Bayesian OCR
  51. The part of Navier-Stokes no one is talking about
  52. AI is an intelligence multiplier
  53. A 50-year-old computer-assisted proof
  54. Navier-Stokes in the news
  55. earlier post
  56. next post
  57. Computing a lower bound on matrix rank
  58. New RSA number factored
  59. Hugging Face Easter Egg
  60. Patented application of linear algebra
  61. Making the unnecessary easier
  62. Second solutions
  63. Junk solutions
  64. What is the quality of software that AI writes?
  65. previous post
  66. extra care
  67. three-term recurrence
  68. The von Mises-Fisher distribution
  69. Why special function terminology is arcane
  70. What exactly is modified about a modified Bessel function?
  71. Coming soon
  72. The difference orbit inclination makes
  73. How would you know whether an ancient culture had zero?
  74. AI-generated ASCII diagrams
  75. Big little hexagon
  76. graph imbalance theorem
  77. Mean distance to the sun
  78. Proportion of 1s in a Hadamard matrix
  79. Compressing a Hadamard matrix
  80. Probability of correcting errors
  81. Constructing Hadamard matrices
  82. next post
  83. Hadamard Codes and Sphere Packing
  84. Cryptic but consistent
  85. Manually unbreakable cryptography
  86. Dogs and fat tails
  87. Inverse differential equations
  88. Learning from historical mistakes
  89. this post
  90. DNA and Bessel functions
  91. next post
  92. How not to calculate cosine
  93. Corrupted apostrophes
  94. Calculating log(1000!)
  95. previous post
  96. Why polynomial coefficients
  97. A few weeks ago
  98. Brace expansion
  99. RSA munitions T-shirt
  100. From Kepler to Bessel
  101. Mr. Bessel’s eponymous functions
  102. The mythology of category theory
  103. The nonlinear pendulum equation
  104. Intersecting spheres and GPS
  105. Roman moon, Greek moon
  106. cheating
  107. How much precision can you squeeze out of a table?
  108. Shell variable ~-
  109. Certified Fibonacci numbers
  110. Satellites have a lot of room

2025 29

  1. Automation and validation
  2. Fit logistic curve
  3. The navigational triangle
  4. Line of position
  5. Lews & Clark navigation
  6. Four generalizations of the Pythagorean theorem
  7. Analog of Heron’s formula for a sphere
  8. Turning trig identities into Fibonacci identities
  9. Time needed to factor large integers
  10. Minimalist Mandelbrot set
  11. Randomly generated dragon
  12. Uppercase eszett
  13. Martin Gardner’s RSA article
  14. Lewis Carroll and zero knowledge proofs
  15. Machine learning by satisfiability solving
  16. Monero’s elliptic curve
  17. Analogs of binomial coefficients
  18. The ellipse hidden inside Pascal’s triangle
  19. Effective graph resistance
  20. partitioned matrix
  21. trinomial triangle
  22. Formulating the eight queens problem as a SAT problem
  23. Bell’s triangle
  24. Lessons learned using the Z3 SAT/SMT solver
  25. Unicode, Tolkien, and Privacy
  26. Unicode surrogates
  27. Max and min orbital speed
  28. Sparse binary Pythagorean triples
  29. Rsa factoring

2024 7

  1. Starlink configurations
  2. Npi number
  3. Using a table of trig functions
  4. Using a table of logarithms
  5. FFT and quadratic reciprocity
  6. Bessel zero spacing
  7. Straddling checkerboard

2023 20

  1. ASCII armor
  2. What can you learn from a phone number?
  3. good faith
  4. Prime numbers simple groups
  5. DFT conventions
  6. spherical coordinates
  7. Traveling salesman tour of Texas
  8. spherical cap
  9. Random points hypersphere orthant
  10. Cosine similarity does not satisfy the triangle inequality
  11. Angles between words
  12. Generating and inspecting an RSA key
  13. this post
  14. Useful de
  15. Equation of a circle through three points
  16. Productive productivity
  17. Category theory without categories
  18. Credit card checksum
  19. Playfair cipher
  20. Van Aubel’s theorem

2022 15

  1. Napoleon’s theorem
  2. Posts on ellipses
  3. multiset
  4. Directrix of a conic
  5. Making flags in Unicode
  6. Prevent characters from displaying as emoji
  7. medical procedure code
  8. law of cosines on a sphere
  9. Memorizing the ASCII table
  10. Projective duality
  11. inversion
  12. Why a slide rule works
  13. Fourier transform
  14. Phone tones inn musical notation
  15. Modal logic and science fiction

2021 9

  1. When do two-body systems have stable Lagrange points?
  2. Naming and numbering modal logics
  3. Finding L1 and L2
  4. partial function
  5. Vigenère cipher
  6. Major memory system telephone keypad
  7. The fractal nature of Brownian motion
  8. Duodecimal vs. Hexadecimal
  9. A few years ago

2020 11

  1. When are formal methods worth the effort?
  2. How big is the monster?
  3. The worst tool for the job
  4. Hadamard’s determinant inequality
  5. Hadamard’s Dirichlet energy example
  6. Sierpiński triangle
  7. Kronecker product
  8. Feistel network
  9. Adfgvx
  10. Odd numbers in Pascal’s triangle
  11. Stable recurrence relations

2019 9

  1. Golay code used in Voyager
  2. Lissajous curves and knots
  3. Harmonographs
  4. Detecting errors with the four color theorem
  5. Vehicle Identification Number checksum
  6. Elliptic curve p 384
  7. What is an elliptic curve?
  8. RSA implementation flaws
  9. Stigler’s law of eponymy

2018 4

  1. Modal logic and cybersecurity
  2. Overlaps in the CFSG
  3. Orders of finite simple groups
  4. Fibonacci meets Pythagoras

2017 3

  1. probability
  2. Function on cover of abramowitz stegun
  3. Visualizing graph spectra

2016 2

  1. Formal methods let you explore the corners
  2. Ascii art diagrams in emacs org mode

2015 2

  1. The FFT and big data
  2. Why isn’t everything normally distributed?

2014 3

  1. clever tricks
  2. Engineering a waterpark
  3. Pi and The Raven

2013 4

  1. This post
  2. this post
  3. The seven color map theorem
  4. Orwellian vs. Huxleyian

2011 1

  1. A Bayesian view of Amazon resellers

2010 3

  1. Maybe you only need it because you have it
  2. small angle
  3. Just-in-case versus Just-in-time

2009 4

  1. How many trig functions are there?
  2. Power laws and the generalized CLT
  3. Metabolism and power laws
  4. Anatomy of a floating point number