Geometer's Notebook

8/24/13

Thales R. Angles & Circles
Thales R. Angles & Circles
Pythagorean Triangles
Pythagorean Circles
Completing the Square
There is a real appeal to solving Algebra through Geometry!

Binomial Square & Cube, Trinomial Square
Binomial to the Fourth Power - via Pascal!
Kai's method for constructing a square on a given line - neat!
The students came up with three or four different methods of their own (using string and chalk on the blacktop) - I particularly liked this one!

Area of a Regular Polygon
Both of these are, as far as I know, original drawings.

Quite chuffed that, after years of learning from books, I am developing a capacity to work this stuff out for myself!  

I am sure that, in terms of world knowledge, this is not a new discovery, but the formula given above for the area of any regular polygon is something I was searching for and was able to come to by myself!

(. . . but I am still working on a formula for the radius of the incircle)

Area of a Regular Polygon - Triangle
Also quite clear from the above that similar triangles with 1/2 length edges have 1/4 the area.

The following are developed from an excellent little paper I found here!

Area of a Pythagorean Triangle (two methods)
Algorithm for producing Pythagorean Triangles
Table so useful I am posting a blank for you to play with in the "Downloads" section here! 

blank
m = 10
m = 10, n = 5
I was initially quite excited by the 100, 75, 125 triangle and went straight into construction without realizing that these proportions would reduce to something already very familiar . . . . .

. . . . but in doing so discovered that standard U.S. Letter sized paper is a basic Pythagorean Triangle with an even 1/2" margin - who knew? 

Felix Culpa!

 


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Excessive Space

8/2/13

The logical proof that there can only be five regular solids is as old as Plato (with deference to Kepler, who I haven't got to yet) but when you set out to make a few of them as toys for a newborn you never know where they'll lead you next . . . .

Platonic Family
. . . having made the five "classical" forms, I decided I might as well continue with the triangles to create the "proof" that these were the only possible regular solids . . . .

Triangles 1 - 6
. . . and then kept going . . . .

. . . . and suddenly the world gets very interesting and I have to start working in cardboard . . . .

 . . . which takes me from traditional plane and solid geometry into a world of petticoats, curtains, lettuce leaves and radiators that seems to have some pretty interesting properties of its own!

Here's the numbers:

(apart from the missing ones, which are: 360, 540, 720, 1,080)

And here's the full set, including pentagons:

Here's 6, 7 & 8

- I woke up with a new stitching idea that would create flat rather than gathered seams that would allow much more freedom for the forms to flow in any direction - if I carried on with blanket stitch (which was great for the solid models) I would just get tighter and tighter scallops. 

Here's two views of the form with 8 triangles (420 degrees = 1 1/3 circles in the space of 1) showing nice flexible curves!

I am quite excited by the imagination that tomorrows project, folding 720 degrees worth of triangles into 360, will allow me to create an Equator that can simultaneously touch both North and South Poles!

Here's what I imagine:

Oodles of progress since the last post, mostly documented in the Platonic Softies, Excessive Space and new container Progressive Geometry Galleries, but here's an interesting thing:

 . . . which I consider to be quite lovely, was the first form that "fell into my hands" after constructing 1080 degrees = 10 Pentagons . . .

. . . but then I thought about things logically (in relation to previous imaginations and the three planes of space) and rearranged things ca:

. . . .which is consistent and fits with the overall scheme . . .

. . . but I still think there's something quite grand about that first one!

 


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Previously published:

All 28 blog entries

Here are some of the ideas that I have been exploring.

Please let me know if there's anything you want to correct/find interesting/would like a copy of - or to purchase/participate in etc.

 Philip James GuestLos Angeles, CA310.383.2327

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