Solved: Implicit derivative?

rking-2 · ‎Dec 19, 2015

How do I perform Implicit Derivative in MathCad?

I am trying to use MathCad Prime to solve an implicit derivative but I have no idea how I could do it. It seems to only solve a normal differentiation with only one variable.

Example:

x^2+y^2=25

dy/dx = -y/x

How do I get MathCad to work properly with implicit derivative?

Thanks!

Werner_E · ‎Dec 21, 2015

Mark Gase wrote:

I didn't know Mathcad could solve this way. To take it one step further, you can solve for dy/dx:

Yes and we don't even need to tamper with the original equation:

OR

OR better

Werner

P.S.: If you encounter problems or get 0 as result, check the labels of your variable and function names. Prime automatic labeling really is erroneous and annoying.

View solution in original post

MJG · ‎Dec 21, 2015

Please post only once.

All, refer to the other post: https://community.ptc.com/t5/PTC-Mathcad/Help-with-implicit-differentiation/td-p/222787

rking-2 · ‎Dec 21, 2015

Thank you Mark.

But in Mathcad Prime I can't open .xmcd file and I can´t convert to .mcdx.

Werner_E · ‎Dec 21, 2015

rking-2 wrote:

Thank you Mark.

But in Mathcad Prime I can't open .xmcd file and I can´t convert to .mcdx.

If you have a valid license for Prime, this license is also valid for Mathcad 15, so if you want to be able to convert files from MC15 and older to Prime format, you may download MC15 here -> Download PTC Mathcad 15.0 Free | PTC

It may be worth it and you need it to be able to do the conversions.

WE

Werner_E · ‎Dec 21, 2015

Why don't you attach a worksheet and screenshots of your attempts so we can see better what you are trying to do.

1) Mathcad unfortunately can't handle implicit functions, so you have to create one term by subtraction 25 from the LHS

2) You have to tell Mathcad that y ist a function dependend on x by writing y(x)

Hope this is what you are looking for.

WE

MJG · ‎Dec 21, 2015

I didn't know Mathcad could solve this way. To take it one step further, you can solve for dy/dx:

Werner_E · ‎Dec 21, 2015

Mark Gase wrote:

I didn't know Mathcad could solve this way. To take it one step further, you can solve for dy/dx:

Yes and we don't even need to tamper with the original equation:

OR

OR better

Werner

P.S.: If you encounter problems or get 0 as result, check the labels of your variable and function names. Prime automatic labeling really is erroneous and annoying.

rking-2 · ‎Dec 21, 2015

Many thanks Werner, is so usefull your answer.

rking-2 · ‎Dec 21, 2015

Thank you all, I will be more careful to publish my questions.