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Re: PolarPlot

• To: mathgroup at smc.vnet.net
• Subject: [mg87775] Re: PolarPlot
• From: dh <dh at metrohm.ch>
• Date: Wed, 16 Apr 2008 22:31:45 -0400 (EDT)
• References: <ftmu5p$50d$1@smc.vnet.net> <ftv938$80f$1@smc.vnet.net> <fu1u66$oom$1@smc.vnet.net>

Hi Helen,

just saw your reply. A coordinate system as you propose would assign 

more than one coordinate tuple to any point. Although I can see 

aplications in graphics (cycloids...), I do not think that this makes 

life easier for calculations. There are enough problems with unique 

maps, no need to make artificial ones.

Daniel



Helen Read wrote:

> dh wrote:

>> Hi Bruce,

>>

>> the radius in polar coordinates has to be real and positive. Therefore, 

> 

> Actually, no. In polar coordinates r is a *directed* distance, which may 

> be positive or negative.

> 

>> r=Sqrt[Cos[phi]] can not be the correct formula, we would get imaginary 

>>

>> values. To prevent this, we may e.g. write: r=Sqrt[Abs[Cos[phi]] what 

>>

>> gives the plot you are looking for.

>>

>> hope this helps, Daniel

>