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MathGroup Archive 2006

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Re: Sin[30*Degree] vs Sin[29*Degree]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72090] Re: Sin[30*Degree] vs Sin[29*Degree]
  • From: Heiko Damerau <heiko.damerau.news at cern.ch>
  • Date: Mon, 11 Dec 2006 04:55:26 -0500 (EST)
  • Organization: CERN News
  • References: <elglnb$h7f$1@smc.vnet.net>

Dear Steven,

     The behaviour of Mathematica is perfectly consistent. It depends on 
whether you look for an exact or for a numerical result.

     Sin[30*Degree] is indeed 1/2 and this result is exact. However, for 
Sin[29*Degree] or Sin[31*Degree] Mathematica cannot find any exact 
solution and just keeps the expression unevaluated. If you want the 
numerical result, ask e.g. for N[Sin[29*Degree]]. By typing 
Sin[29*Pi/180.] you are asking for the numerical result as 180. <- with 
a dot at the end means the numerical value 180 and Mathematica will 
automatically perform a numerical calculation. Try to ask Mathematica 
for the exact result of Sin[29*Pi/180] and you will see that the 
expression is kept as well as Sin[29*Degree]. Again, this time 
Mathematica tries to find the exact solution... which doesn't exist.

Hope this helps,
Heiko


Steven Shippee schrieb:
> What is happening here:
> 
> Sin[30*Degree]
> Sin[31*Degree]
> Sin[29*Degree]
> which makes it appear that only the first line of input works?
> 
> However, if I do something like:
> 
> \!\(Sin[\(29*Pi\)\/180. ]\)
> 
> I get the expected result ... I'm sure it is me, what am I missing in that I 
> think I am not seeing consistent behavior?
> 
> Thanks in advance,
> 
> Steven Shippee
> 
> slshippee at comcast.net
> 
> 
> 
> 


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