Re: LOGO-L> elipse

[Jeff <jeffr@mugc.cc.monash.edu.au>]

On Wed, 11 Feb 1998, Richard Impey wrote:
> A fellow teacher requires a MicroWorlds procedure for drawing an elipse so
> as to create a simulation of planets circling the sun. Is it possible to
> also have the "earth" turtle grow and shrink as it orbits??
Richard

the 'classic' turtle geometry ellipse is:

to ellipse :size :eccentricity
make "n 0
repeat 360
[rt :n fd :size lt :n lt :n fd :size*:eccentricity rt :n make "n :n+1]
end

...though the figure you get will lokk like an ellipse, when you analyse 
the motion of the turtle, it is following an epicycle. This has a nice 
resonance, as pre-copernican astronomy 'saw' planetary motion as epicyclical.

Turtles can be magnified in Microworlds by using SETSIZE

Jeff Richardson
Faculty of Education
Monash University
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