John D. Cook
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johndcook.mathstodon.xyz.ap.brid.gy
John D. Cook
@johndcook.mathstodon.xyz.ap.brid.gy
150 followers 0 following 340 posts
Consultant in applied mathematics and data privacy

https://www.johndcook.com

[bridged from https://mathstodon.xyz/@johndcook on the fediverse by https://fed.brid.gy/ ]
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johndcook.mathstodon.xyz.ap.brid.gy
Monero subaddresses
https://www.johndcook.com/blog/2025/11/28/monero-subaddresses/
Monero logo
November 28, 2025 at 9:37 PM
johndcook.mathstodon.xyz.ap.brid.gy
A triangle whose interior angles sum to zero

https://www.johndcook.com/blog/2025/11/28/tricusp-triangle/
November 28, 2025 at 5:54 PM
johndcook.mathstodon.xyz.ap.brid.gy
There are multiple equivalent expressions for the metric on the Poincare half plane, but they all look different.

https://www.johndcook.com/blog/2025/11/27/hyperbolic-metric-formulas/
November 27, 2025 at 1:28 PM
johndcook.mathstodon.xyz.ap.brid.gy
A TV tuned to a dead channel

https://www.johndcook.com/blog/2025/11/24/tv-tuned-to-a-dead-channel/
November 25, 2025 at 1:27 AM
johndcook.mathstodon.xyz.ap.brid.gy
How stealth addresses work in Monero
https://www.johndcook.com/blog/2025/11/24/monero-stealth-addresses/
Alice's Restaurant
November 24, 2025 at 5:31 PM
johndcook.mathstodon.xyz.ap.brid.gy
The sum of the reciprocals of consecutive integers is never an integer.

József Kürschák, 1908.
November 19, 2025 at 12:49 PM
johndcook.mathstodon.xyz.ap.brid.gy
Five posts on Pythagroean triples

https://www.johndcook.com/blog/2025/11/18/pythagorean-triples-2/
November 18, 2025 at 1:20 PM
johndcook.mathstodon.xyz.ap.brid.gy
Elliptic curve pairings in cryptography

https://www.johndcook.com/blog/2025/11/16/elliptic-curve-pairings/
Robin Williams as the genie from Alladin doing his William F Buckley imitation.
November 16, 2025 at 8:33 PM
johndcook.mathstodon.xyz.ap.brid.gy
Four generalizations of the Pythagorean theorem

https://www.johndcook.com/blog/2025/11/13/pythagorean-generalizations/
November 13, 2025 at 3:31 PM
johndcook.mathstodon.xyz.ap.brid.gy
The graph below appears to show that the correlation between two stocks peaks about every 50 days. But this is purely an analysis artifact. The two series are in fact independent random walks. Shows how analysis can be misleading.

https://www.johndcook.com/blog/2025/11/09/rolling-correlation/
November 9, 2025 at 7:03 PM
johndcook.mathstodon.xyz.ap.brid.gy
There's talk of building gigawatt data centers. How much is a gigawatt? https://www.johndcook.com/blog/2025/11/07/how-much-is-a-gigawatt/
November 7, 2025 at 2:17 PM
johndcook.mathstodon.xyz.ap.brid.gy
The sum of the inradii in any triangulation of a cyclic polygon is the same for all triangulations.

https://www.johndcook.com/blog/2025/11/05/japanese-polygon-theorem/
Two examples
November 5, 2025 at 12:03 PM
johndcook.mathstodon.xyz.ap.brid.gy
The Pythagorean theorem squares the lengths of the sides in a right triangle. An analogous theorem squares the areas of faces of a right tetrahedron and generalizes to higher dimensions.

https://www.johndcook.com/blog/2025/11/03/de-gua/
November 3, 2025 at 4:44 PM
johndcook.mathstodon.xyz.ap.brid.gy
The anti-Smith chart
https://www.johndcook.com/blog/2025/11/02/anti-smith-chart/
November 2, 2025 at 10:14 PM
johndcook.mathstodon.xyz.ap.brid.gy
Impedance and triangular numbers

https://www.johndcook.com/blog/2025/11/02/impedance-and-trianglular-numbers/
November 2, 2025 at 1:13 PM
johndcook.mathstodon.xyz.ap.brid.gy
Capitalization impacts the size of QR codes

https://www.johndcook.com/blog/2025/10/31/smaller-qr-codes/
October 31, 2025 at 3:55 PM
johndcook.mathstodon.xyz.ap.brid.gy
An ancient generalization of Pythagorean theorem

https://www.johndcook.com/blog/2025/10/30/apollonius-theorem/
October 30, 2025 at 1:11 PM
johndcook.mathstodon.xyz.ap.brid.gy
Comparing physical keys and encryption keys

https://www.johndcook.com/blog/2025/10/29/physical-keys-encryption-keys/
Metal key with 55 cuts
October 29, 2025 at 3:20 PM
johndcook.mathstodon.xyz.ap.brid.gy
Why and how Bitcoin uses Merkle trees

https://www.johndcook.com/blog/2025/10/28/bitcoin-merkle-trees/
October 28, 2025 at 2:09 PM
johndcook.mathstodon.xyz.ap.brid.gy
How blocks are chained in a blockchain, in full detail

https://www.johndcook.com/blog/2025/10/27/blockchain/
October 27, 2025 at 4:00 PM
johndcook.mathstodon.xyz.ap.brid.gy
Follow up to my post on the Smith chart:
How to adjust the spacing of the circles

https://www.johndcook.com/blog/2025/10/25/smith-chart-spacing/
October 25, 2025 at 2:57 PM
johndcook.mathstodon.xyz.ap.brid.gy
New post: The Smith chart

https://www.johndcook.com/blog/2025/10/23/smith-chart/
October 23, 2025 at 2:24 PM
johndcook.mathstodon.xyz.ap.brid.gy
Randomly generating points in Colorado

https://www.johndcook.com/blog/2025/10/22/generating-random-points-in-colorado/
October 22, 2025 at 1:07 PM
johndcook.mathstodon.xyz.ap.brid.gy
Distribution of the correlation coefficient

https://www.johndcook.com/blog/2025/10/20/distribution-of-correlation/
October 20, 2025 at 12:16 PM
johndcook.mathstodon.xyz.ap.brid.gy
Converting between nines and sigmas

https://www.johndcook.com/blog/2025/10/18/quality-metrics/
October 18, 2025 at 7:55 PM