Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!uxc.cso.uiuc.edu!garcon!vega!george
From: george@vega (John George)
Newsgroups: comp.graphics
Subject: Re: Mathematica
Message-ID: <1879@garcon.cso.uiuc.edu>
Date: 29 Aug 89 16:31:48 GMT
References: <58589@tut.cis.ohio-state.edu>
Reply-To: george@symcom.math.uiuc.edu (John George)
Organization: Dept. of Mathematics, Univ. of Illinois at Urbana-Champaign
Lines: 26

In article <58589@tut.cis.ohio-state.edu> <ray@cis.ohio-state.edu> writes:
>(hope both these newsgroups are appropriate here)
>
>So, I went out yesterday, and purchased mathematica for my MacII.
>does anyone know what it's good for?  (Ok I can read the instructions,
>anyone have any novel ideas, interesting custom packages, hints & tips, 
>any idea why I keep crashing out with an id#15 error?)
>
>Thanx
>Will Ray

 spirograph[p_Integer, q_Integer, a_, start_:0, opts___Rule] :=
	Block[ {m = (q-p)/q, n = (q-p)/p, x = Cos[start], y = Sin[start]},
        ParametricPlot[{
			x(m Cos[t] + a Cos[n t]) - y(m Sin[t] - a Sin[n t]),
        		y(m Cos[t] + a Cos[n t]) + x(m Sin[t] - a Sin[n t])
			},
        {t, 0, 2 p Pi}, opts, AspectRatio -> Automatic,
        PlotPoints -> 24, Axes->None]
	];
spirograph::usage="spirograph[p, q, a, rot:0, (optionlist)]
displays the spirograph design formed by an outer wheel of
radius one and an inner wheel of radius p/q, with a pen placed 
a units from the center; beginning at rot radians above the 
x-axis.";
Null;