@>exp on trig functions

[electroscott]

Greetings,

I usually use an HP50G but bought a TI Nspire for its ease in
visualizing geometric/trig relations, as I used it for a robotics
control class to handle DH parameters (I was able to draw vectors and
such easier on it than the 50G). After that class ended, I pretty
much didn't use the calc anymore, but with the CX CAS coming I have
been revisiting the machine.

One thing I like to use the calc for is to use it to manipulate
equations instead of using a pencil and paper. Toward this end, I
cannot find a way to express trig terms such as "sin(x)" in their
exponential form. Some of the things I have tried are:

(1) sin(x)@>exp.
(2) sin(x)|sin(x)=1/(2i)*(exp(i*x)-exp(-i*x))
(3) string(1/(2i)*(exp(i*x)-exp(-i*x)))
etc.

Even the "string(...)" part returns "sin(x)" in string form, so the
command line interpreter is converting my exp sine equivalent back to
sin(x) before getting converted to a string.

Some may wonder why I want this to work (as it does on the HP50G where
I can express things in terms of COS, SIN, TAN, EXP/LN, etc.). It is
simply to help visualize relations (esp. in exp mode) where I can
begin to simplify terms and collect terms like exp. Of particular
importance is when I'm working with Fourier transform pairs or Laplace
transform pairs and want to manipulate sin/cos in terms of exp.

Since I'm struggling with the learning curve of this calculator (gosh,
it's a steep one!) I may be missing something obvious. Does anyone
have any suggestions on telling the calc to not automatically convert
exp functions back to trig functions?

Thanks,
--Scott

[Jimmy Fullerenex]

Maybe switch to some other modes and change a couple of settings?

Cheers,

Jimmy Fullerenex

2011/5/29 electroscott <electr...@gmail.com>

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[electroscott]

I've tried a few things like complex format = rectangular and polar
(as opposed to real), so I'll keep fiddling around with other settings
as I find them.

Thanks for the reply.

--Scott

On May 28, 11:10 pm, Jimmy Fullerenex <smoat...@gmail.com> wrote:
> Maybe switch to some other modes and change a couple of settings?
> Cheers,
> Jimmy Fullerenex
>

> 2011/5/29 electroscott <electrosc...@gmail.com>

[Nelson Sousa]

The Nspire cas doesn't do that. You can't specify what kind of output you want, which is too bad actually. I totally understand the need to sometimes write everything in terms of exp instead of sin and cos (likewise, writing everything in terms of sin only and replace all instances of cos).

--
Nelson

[electroscott]

Thanks for the reply. It looks like sometimes it does *some* of what
I need. For example, from the Nspire CAS reference guide, p43, there
is an example of "2sinh(x)@>exp" showing as "e^-x*(e^2x-1)".
Likewise, for @>cos, it shows "(sin(x)^2)@>cos" as "1-(cos(x)^2)".

--Scott

On May 29, 9:01 am, Nelson Sousa <nso...@gmail.com> wrote:
> The Nspire cas doesn't do that. You can't specify what kind of output you want, which is too bad actually. I totally understand the need to sometimes write everything in terms of exp instead of sin and cos (likewise, writing everything in terms of sin only and replace all instances of cos).
>
> --
> Nelson
>

[Nelson Sousa]

The set of precedences between equivalent forms of the same
expressions is fixed. Sin and Cos as used instead of complex
exponentials, real exponentials are used instead of sinh and cosh,
powers with fraction exponents instead of roots, natural log instead
of log_10, etc.

Unfortunately you can't change that order and say you prefer a different form.

Nelson

[electroscott]

That makes sense now. Thanks.