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My apologies.  You are right—I thought I was getting the line using either one, but when I replaced cos (degrees) with COS(radians), the line curved.
<div class="">MY BAD!</div>
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<div class="">Z</div>
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Zbigniew Nitecki<br class="">
Department of Mathematics<br class="">
Tufts University<br class="">
Medford, MA 02155<br class="">
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telephones:<br class="">
my office     (617) 627-3843<br class="">
dept. off.    (617) 627-3234<br class="">
dept. fax    (617) 627-3966<br class="">
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<a href="http://sites.tufts.edu/znitecki/" class="">http://sites.tufts.edu/znitecki/</a></div>
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<div class="">On Sep 10, 2018, at 12:16 PM, Michael Sharpe <<a href="mailto:msharpe@ucsd.edu" class="">msharpe@ucsd.edu</a>> wrote:</div>
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<blockquote type="cite" class="">On Sep 10, 2018, at 8:27 AM, Nitecki, Zbigniew H. <<a href="mailto:Zbigniew.Nitecki@tufts.edu" class="">Zbigniew.Nitecki@tufts.edu</a>> wrote:<br class="">
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What is wrong here?  using pstricks, pst-plot and \pst-math, the following command<br class="">
<blockquote type="cite" class="">\parametricplot[plotstyle=curve, plotpoints=50]{-1.8}{1.8}{0.25 t Pi mul mul cos t}<br class="">
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which should create a curve opening left, creates a vertical line.<br class="">
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Minimal example:<br class="">
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Remember that cos in Postscript expects its argument in degrees, so you may wish to use instead<br class="">
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\parametricplot[plotstyle=curve, plotpoints=50]{-1.8}{1.8}{0.25 t 180 mul mul cos t}<br class="">
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Michael<br class="">
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