Geometry Joys, Math and Computer Science Everywhere, Math Tricks, Murderous Maths, Notes on everyday life, Simon teaching, Simon's sketch book

Sums of consecutive numbers

While waiting to pick his little sister up from a ballet class, Simon explaining general algebraic formulas to calculate the sums of consecutive numbers. He derives the formulas from drawing the numbers as dots forming certain geometric chapes.
consecutive integers
consecutive odd integers
Crafty, Geometry Joys, Good Reads, Logic, Murderous Maths, Simon teaching, Simon's sketch book

Attractiveness vs. Personality

Debunking the stereotype that all attractive guys/girls are mean, something Simon has learned from MajorPrep and the How Not to Be Wrong book by Jordan Ellenberg. The slope in dark blue pen shows our scope of attention, a pretty narrow part of the actually diverse field of choices.
art, Crafty, Geometry Joys, Math and Computer Science Everywhere, Math Riddles, Murderous Maths, Notes on everyday life, Simon makes gamez, Simon teaching, Simon's sketch book, Together with sis

Math puzzles: Is it Possible?

Simon has been fascinated by these possible-impossible puzzles (that he picked up from the MajorPrep channel) for a couple of days. He prepared many paper visuals so that Dad and I could try solving them. This morning he produced this beautiful piece of design:

Simon showing one of the puzzles to another parent while waiting for Neva during her hockey training
Simon’s original drawing of the doors puzzle. The solution of the puzzle is based on graph theory and the Eulerian trail rule that the number of nodes with an odd degree should be either 0 or 2 to be able to draw a shape without lifting your pencil. The number of rooms with an odd number of doors in the puzzle is 4 (including the space surrounding the rectangle), that’s why it’s impossible to close all the doors by walking though each of them only once.
Simon explaining odd degree nodes
Computer Science, Electronics, Geometry Joys, Logic, Math and Computer Science Everywhere, Murderous Maths, Notes on everyday life, Simon's sketch book, Trips

Doing math and computer science everywhere

One more blog post with impressions from our vacation at the Cote d’Azur in France. Don’t even think of bringing Simon to the beach or the swimming pool without a sketchbook to do some math or computer science!

This is something Simon experimented with extensively last time we were in France. Also called the block-stacking or the book-stacking problem.
Simon wrote this from memory to teach another boy at the pool about ASCII binary. The boy actually seemed to find it interesting. A couple days later two older boys approached him at the local beach and told him that they knew who he was, that he was Simon who only talked about math. Then the boys ran away and Simon ran after them saying “Sorry!” We have explained to him that he doesn’t have to say sorry for loving math and for being the way he is.
Drinking a cocktail at the beach always comes with a little lecture. This time, the truth tables.
Coding, Contributing, Geometry Joys, Math Tricks, Murderous Maths, Python, Simon teaching, Simon's Own Code, Simon's sketch book

Why the Golden Ratio and not -1/the Golden Ratio?

Take any real number and call it x. Then plug it into the equation f(x) = 1 + 1/x and keep doing it many times in a row, plugging the result back into the equation.

At some point you will see that you arrive at a value that will become stable and not change anymore. And that value will be… φ, the golden ratio!

But this equation also has another answer, -1/φ. If you plug that value into the equation, it will be the same, too. The real magic happens once you have rounded the -1/φ down (or up), i.e. once what you plug into the equation is no longer exactly -1/φ. What happens is that, if you keep going, you will eventually reach… φ as your answer!

Simon saw this interesting fact in a video by 3Blue1Brown and then came up with a proof as to why it happens.

Simon also sketched his proof in GeoGebra: https://www.geogebra.org/classic/zxmqdspb

Crafty, Geometry Joys, Math Tricks, Murderous Maths, Simon teaching, Simon's sketch book

Inscribed angle theorem

“It reveals itself once you complete the rectangle to find the centre. Because, of course, the diagonal passes through the centre once you inscribe a rectangle inside the circle, because of the symmetry”.
Tiling the quadrilaterals Simon has crafted applying the inscribed angle theorem.
Tiling the “shapes generated by the inscribed angle theorem”
“The theorem says that if you have a circle and just three random points on it, then you draw a path between te first point to the second, to the centre, to the third point and back to the first point”.
art, Coding, Geometry Joys, Murderous Maths, Museum Time, Notes on everyday life, Together with sis, Trips

Back at Stedelijk

As for Morellet’s RGB colored cells, very inspiring for a sandpiles coding project. (The photographs don’t convey half of the effect the original canvasses invoke. Morellet’s cells actually appear to be moving when you gaze at the original).
Installation by Barbara Kruger
Installation by Barbara Kruger
Read this poem from top to bottom and it’s depressing, from bottom to top and it’s empowering.
Geometry Joys, Math Tricks, Murderous Maths, Simon teaching, Simon's sketch book

Triangular, Square, Pentagonal, Hexagonal Numbers

Applying one of his favorite materials – checkers – Simon showed me the tricks behind polygonal numbers. The numbers written in pen (above) correspond to the actual triangle number (red rod) and the row number (blue rod).
Square numbers
Pentagonal numbers
And the next pentagonal number
(Centered) Hexagonal numbers
Fragment of the next (centered) hexagonal number
The following morning I saw that Simon came up with these general formulae to construct square, pentagonal and hexagonal numbers using triangle numbers. The n stands for the index of the polygonal number. Later Simon told me that he had made a mistake in his formula for the hexagonal numbers: it should not be the ceiling function of (n-1)/2, but simply n-1, he said.

I asked Simon to show me how he’d come up with the formulae:

Here is a square number constructed of two triangle numbers (the 5th and the 4th, so the nth and the n-1st)
The working out of the same construction. In the axample above n equals 5, so the 5th square number is indeed 25.
The nth pentagonal number constructed using three triangle numbers: the nth triangle number, and two, n-1st triangle numbers.
The working out of the pentagonal number formula
The nth hexagonal number
The formula for calculating the nth hexagonal number from six n-1st triangle numbers plus 1. (Simon later corrected the (n+1) into (n-1)).
Crafty, Geometry Joys, motor skills, Murderous Maths, Simon teaching, Simon's sketch book

A Square Triangle?

Simon explains what Gaussian formula is to check a shape’s curvature and shows how to make a triangle with three 90° angles. Or is it a square, since it’s a shape with all sides equal and all angles at 90°? He also says a few words about the curvature of the Universe we live in.

Almost everything he shares in this video Simon has learned from Cliff Stoll on Numberphile:
https://www.youtube.com/watch?v=n7GYYerlQWs
https://www.youtube.com/watch?v=gi-TBlh44gY

Geometry Joys, Murderous Maths

Parabolas are special

At the bakery, Simon tells me: “Parabola is the only shape that’s both an ellipse and a hyperbola (at least in a projective plane, which means that you can have a point at infinity). There are three ways to draw a parabola:

1. Graph y =x^2

2. Slice a cone parallel to its slope.

3. (Which we don’t really care about) Throw something.”

We buy modeling clay on the way home. He tries to reconstruct what he said about a parabola as a cross section of a cone.