python fun geometry
Recently, i got a lot of fun going through the examples of turtle geometry in Abelson & Di Sessa original book. (As already stated in previous thread by me) Also, i started translating from logo to python all the examples in the first chapter. I am over the third paragraph at the moment. If anyone is interested in receiving the first whole bunch of these nice codes, just tell me. Now, i have a geometric question about what the authors write: in sec 1.1.2 they say that the following logo code: TO ARCR R DEG REPEAT DEG FORWARD R RIGHT 1 produce a circular arc as output, having "DEG" degrees and "R" radius; and that it's true, actually; if DEG = 180 the arc is a semicircumference and so on... But, the "R" in the code is the single step forward the turtle does in its path so i can't understand how this R can be seen as the radius of the circular arc. Any hint is very appreciated. -- roberto
On Thu, Sep 16, 2010 at 1:46 PM, roberto <roberto03@gmail.com> wrote:
Now, i have a geometric question about what the authors write: in sec 1.1.2 they say that the following logo code:
TO ARCR R DEG REPEAT DEG FORWARD R RIGHT 1
produce a circular arc as output, having "DEG" degrees and "R" radius; and that it's true, actually; if DEG = 180 the arc is a semicircumference and so on...
But, the "R" in the code is the single step forward the turtle does in its path so i can't understand how this R can be seen as the radius of the circular arc. Any hint is very appreciated.
Going forward 1 pixel and then turning 1 degree (and then repeating 360 times) gives you as close to a circle as you can get on the screen. If you were go to forward 2 pixels, the circle will be less smooth, but the radius will be twice the size... and so on... HTH, Vern --
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-- This time for sure! -Bullwinkle J. Moose ----------------------------- Vern Ceder, Director of Technology Canterbury School, 3210 Smith Road, Ft Wayne, IN 46804 vceder@canterburyschool.org; 260-436-0746; FAX: 260-436-5137 The Quick Python Book, 2nd Ed - http://bit.ly/bRsWDW
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roberto -
Vern Ceder