Re: BUG in Calculus`VectorAnalysis` CoordinatesFromCartesian?
- To: mathgroup at smc.vnet.net
- Subject: [mg15042] Re: [mg15010] BUG in Calculus`VectorAnalysis` CoordinatesFromCartesian?
- From: David Withoff <withoff>
- Date: Wed, 9 Dec 1998 04:12:25 -0500
- Sender: owner-wri-mathgroup at wolfram.com
> I worked a little bit with the Calculus`VectorAnalysis package, and
> think I found a minor BUG.
>
> Needs["Calculus`VectorAnalysis`"];
> SetCoordinates[Spherical];
>
> ein={e,45Degree,0Degree};
> CoordinatesToCartesian[ein]
> Out={e/Sqrt[2], 0, e/Sqrt[2]}
>
> CoordinatesFromCartesian[%]
> Out={Sqrt[e^2], ArcCos[e/(Sqrt[2]*Sqrt[e^2])], ArcTan[e/Sqrt[2], 0]}
>
> The 3rd list entry (Pphi) contains the ArcTan with an invalid argument.
>
> Marcus Heidkamp
>
> msheidka at physics.utexas.edu
The result with ArcTan[e/Sqrt[2], 0] is correct. Zero is a valid
argument here. If e is real, ArcTan[e/Sqrt[2], 0] is zero for e>0 and
Pi for e < 0. Perhaps you were thinking of something else.
Dave Withoff
Wolfram Research