Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

** Community Tip** - Learn all about the Community Ranking System, a fun gamification element of the PTC Community.
X

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

May 02, 2020
11:28 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 02, 2020
11:28 AM

Derivative problem

I used the derivative function but now i need to find L how to do it ?

Labels:

4 REPLIES 4

May 02, 2020
08:14 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 02, 2020
08:14 PM

Hi

You need to define values for "U", "R", & "L"

Cheers

Terry

May 02, 2020
09:03 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 02, 2020
09:03 PM

You equation can't be solve by elementary means, so Prime can't find a symbolic solution.

But if you provide values for U, R and t you can get a numerical solution for L:

This is probably not the solution you are looking for, but when forced to switch into float mode, the symbolic will only return one solution with no control over it.

Note that I used the prime operator for the derivative.

Another way would be to use the usual derivative operator as you did and assign the result to a new function (I called it "f1" in the pic below and made it dependent on t AND L).

You may add units and use the numeric "root" command instead of the symbolic solve. Numerical methods like "root" or a solve block a native to Prime and can handle units (the symbolics doesn't know anything about units):

Prime 6 worksheet attached

May 03, 2020
01:54 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 03, 2020
01:54 PM

"You equation can't be solve by elementary means, so Prime can't find a symbolic solution."

Stupid Prime.

Success!

Luc

May 04, 2020
12:00 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 04, 2020
12:00 AM

@LucMeekes wrote:

"You equation can't be solve by elementary means, so Prime can't find a symbolic solution."

Stupid Prime.

LambertW is not "elementary" and can usually only be evaluated numerically

But I second your "Stupid Prime" nonetheless for many other reasons 😉