# Inrtinsic equations

1. Jan 21, 2009

### Fermat

Anyone know of a program/application/applet that will plot/graph intrinsic equations ?
(preferably free)

I've already had suggestions for KmPLot and Maxima, but neither, it seems, can do the job.
KmPLot is mainly for Linux and I'm on Win XP. (also Vista)

2. Jan 21, 2009

### trebmling

Try Origin, it's the best for this. But it is not free.

3. Jan 21, 2009

### Fermat

Thanks. I've downloaded the evaluation copy. But I can't find any reference to "intrinsic" in the help files.. There's nothing in the plot menu about intrinsic equations either.

The intrinsic equaion for the parabola is,

s = a tan(psi) sec(psi) + a log(tan(psi)+sec(psi)).

How would I use Origin to plot this?

TIA

4. Jan 21, 2009

### trebmling

create new graph
go to menu Graph/add function graph/then copy-paste your equations, or use the drop down menu to choose elementary functions to combine them into your formula.

And they have an excellent forum there http://www.originlab.com/forum/default.asp

5. Jan 23, 2009

### Fermat

Thanks for the input Trebmling, but I'm wondering if we have been talking at cross purposes.

An intrinsic equation, of the form s=f(psi), passes through the origin. s is the distance along the curve from the origin to a point of interest and psi (or tan(psi)) is the slope of the curve at the point of interest. (In other words, s and psi are not rectangular/Cartesian coordinates, or polar coordinates.)

I've been to the Origin forum and posted my query there - "how do I use Origin to plot an intrinsic equation?" - using the above description of an intrinsic eqn. I've had no responses.

I can go into Origin, create a new graph, and give a function, which will be F(x)=cos(x), say - a Cartesian equn. I can tell Origin to treat this as a polar eqn. But can I tell Origin to treat it as an intrinsic equation?

This is what I still can't get.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook