Re: A89: user functions


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Re: A89: user functions




> Say I wanted to write a 
> function for multivariable implicit differentiation...a simple example:
> 
> v = r+s, find dv/dt,dr/dt,and ds/dt
> 
> answer: dv/dt = dr/dt+ds/dt (I think that's right,been too long since
> Cal I =P)

Just a question:  Why are you using a function for this?  People are
always underestimating the capabilities of a TI-89.  Just write:

d(v(t)=r(t)+s(t),t)

and the result will come out like this:

d(v(t),t)=d(r(t),t)+d(s(t),t)

(for this simple example)

If you want to get more complicated and solve this for something, and
can't do that yourself - assuming you are one of those usual TI-89 users - you
just have to substitute a variable for what you want to solve for, and voilą!
 You can even do that by writing:

ans(1)|d(r(t),t)=a

Now if that didn't help you, try doing this with the SDK, or worse,
TI-GCC.  (I love that EStack - never used it, but it is probably good for RPN
;-).)

Don't worry about the look of these equations; they look a lot nicer with
Pretty Print.  I cannot guarantee that these work with AMS versions other
than 2.03.  For any further questions, mail me or turn this over to the math
list people.

BTW: Scott, NO!

Sebastian Reichelt

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