Re: How to NOT convert Sin[x]/Cos[x] to Tan[x] ?
- To: mathgroup at smc.vnet.net
- Subject: [mg44823] Re: How to NOT convert Sin[x]/Cos[x] to Tan[x] ?
- From: drbob at bigfoot.com (Bobby R. Treat)
- Date: Wed, 3 Dec 2003 04:24:05 -0500 (EST)
- References: <bq5b08$k05$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Mathematica doesn't compute things so much as apply substitution rules. For Divide there's a rule that says Sin[x_]/Cos[x_]:>Tan[x]. The opposite is also true, so to prevent an infinite loop, Mathematica stops with the simplest expression it can find. Tan[x] is simpler than the other expression (smaller leaf count, smaller tree depth, smaller bytecount, whatever), so that's what it gives you. Ted Ersek recently told us about a package (HoldTemporary) that will help: http://library.wolfram.com/infocenter/MathSource/705/ Bobby AES/newspost <siegman at stanford.edu> wrote in message news:<bq5b08$k05$1 at smc.vnet.net>... > The Mathematica Book says "Mathematica automatically uses functions like > Tan whenever it can" and shows as an example that Sin[x]^2/Cos[x] is > converted to Sin[x] Tan[x] . > > Any simple way to stop this in displaying the output of a symbolic > calculation? > > The obvious attempt of applying /.Tan[x]->Sin[x]/Cos[x] doesn't seem to > do what's wanted. > > [And out of curiousity, WHY does it do this? That is, why is Tan > apparently given a higher priority than Cos?]
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