Implicit differentiation on HP Prime.

[John P]

Hi Everybody,
Does anybody knows how to implicitly differentiate functions on HP Prime?
Thanks.

[Han]

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.

[John P]

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.

[Han]

(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.

[John P]

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.