Implicit differentiation on HP Prime.
12-17-2013, 03:37 AM
Post: #1
 John P Member Posts: 213 Joined: Dec 2013
Implicit differentiation on HP Prime.
Hi Everybody,
Does anybody knows how to implicitly differentiate functions on HP Prime?
Thanks.
12-17-2013, 04:38 AM
Post: #2
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: Implicit differentiation on HP Prime.
When I do:

diff(3*7^x-x*g(x^2),x)

I get:

-x*diff(g(x^2),x)+3*7^x*LN(7)-g(x^2)

which is pretty much correct except it did not simplify diff(g(x^2),x) since it has no idea what g(x) is -- I intentionally left g(x) undefined for this example.

Graph 3D | QPI | SolveSys
12-17-2013, 05:34 AM
Post: #3
 John P Member Posts: 213 Joined: Dec 2013
RE: Implicit differentiation on HP Prime.
Thanks. I tried something similar but I could not solve for diff(y(x),x). I think results with diff(y(x),x) are pretty useless because you can't use them in farther calculations. I hope they will implement implicit differentiation i next ROM update.
12-17-2013, 05:55 AM
Post: #4
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: Implicit differentiation on HP Prime.
(12-17-2013 05:34 AM)John P Wrote:  Thanks. I tried something similar but I could not solve for diff(y(x),x). I think results with diff(y(x),x) are pretty useless because you can't use them in farther calculations. I hope they will implement implicit differentiation i next ROM update.

Use subst() or convert the result into a string with STRING(). Then use REPLACE() and (to replace "diff(y(x),x)" with just "Yy" for example) and then convert back to a symbolic via EXPR() and continue with solving. Just make sure to add single quotes around the string before using EXPR(). You can probably automate this in a program.

Graph 3D | QPI | SolveSys
12-17-2013, 07:47 AM
Post: #5
 John P Member Posts: 213 Joined: Dec 2013
RE: Implicit differentiation on HP Prime.
I can do it manually, it works fine with replace, but I can't make program to do the staff. Always getting an error when exiting program mode.
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