Elliptical orbits for planets

[mwforum@xxxxxxxxxxxxxxxxxx (Dale Reed)]

> The usual method for making an elliptical shaped flower bed in the garden
is to use 3 sticks and a piece of string.

That is what I am attempting to do with MSWLogo.  Does not work for all
flower bed locations and there are no doubt other problems I have not
discovered yet.  Also I want the turtle to stop after the ellipse is
finished.   Dale

to aaa   :focix1   :fociy1  :focix2 :fociy2 :twoA
; aaa  -200 100   100 200  400
cs
pu
setxy :focix1 :fociy1
localmake "foci1 pos
foci
setxy :focix2 :fociy2
localmake "foci2 pos
foci
localmake "dist (distance :foci1) / 2
setheading towards :foci1 fd :dist
rt 90
fd sqrt( :twoA / 2 * :twoA / 2 - :dist * :dist)
rt 90 pd
repeat 8000 [
fd .1
 do.until [localmake "A distance :foci1 localmake "B distance :foci2 rt .01
fd .01 ]
     [ :A + :B < :twoA  ]]
end

to foci
pd
circle 3
pu
end
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$ dale-reed@xxxxxxx    Seattle, Washington USA $