How to calculate derivatives?
02-20-2018, 11:16 AM
Post: #1
 firedwheelman Junior Member Posts: 2 Joined: Nov 2017
How to calculate derivatives?
I am having a hard time figuring out how to calculate derivatives on the HP Prime. Do I need to download a certain program or can I compute it directly in CAS mode?
02-20-2018, 04:55 PM (This post was last modified: 02-20-2018 04:59 PM by TheKaneB.)
Post: #2
 TheKaneB Member Posts: 175 Joined: Jul 2014
RE: How to calculate derivatives?
On the first row of keys, under the black portion, you have the following keys: Vars, Tools and Templates (there are graphic icons, not actual words on them).

Click the templates button, select the d/dx template and enter your function by filling up the template provided. Enjoy!

In Home view you will get a numerical approximation, while in CAS mode if you have exact mode active you will get a symbolic answer.

Software Failure: Guru Meditation

--
Antonio
IU2KIY
02-20-2018, 05:09 PM (This post was last modified: 02-20-2018 05:13 PM by DrD.)
Post: #3
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
RE: How to calculate derivatives?
Also:

You can use the diff() command (See help): diff(x^2+2*x+c,x) ==> 2*x+2

You can use the apostrophe: (x^2+2*x+c)' ==> 2*x+2
02-20-2018, 06:04 PM
Post: #4
 grsbanks Senior Member Posts: 1,195 Joined: Jan 2017
RE: How to calculate derivatives?
(02-20-2018 05:09 PM)DrD Wrote:  You can use the apostrophe: (x^2+2*x+c)' ==> 2*x+2

You learn something new every day -- I never knew that!
02-20-2018, 10:01 PM (This post was last modified: 02-20-2018 10:01 PM by TheKaneB.)
Post: #5
 TheKaneB Member Posts: 175 Joined: Jul 2014
RE: How to calculate derivatives?
That's very useful! In the function definition of the graph app it doesn't work though. You first have to define your f2:=f1' and then apply it to the graph app like F2(X) = f2(X) in the Symbolic view.

Software Failure: Guru Meditation

--
Antonio
IU2KIY
02-21-2018, 06:50 AM
Post: #6
 cyrille de brĂ©bisson Senior Member Posts: 1,009 Joined: Dec 2013
RE: How to calculate derivatives?
Hello,

' for derivative is a CAS function, not a home function which is why it does not work in the plotting app.

2nd subtility.

The "result" of the derivative function is a function, not the function evaluated at a point!
So, if you define F2 in the symb view as der(F1(X),X) (with der being the derivative symbol), whenever F2 gets evaluated, the der function returns the derivated F1, NOT the numerical result of the evaluation of the derivative of F1!

The proper syntax to get the VALUE of the derivative of a function at a point is: der(F1(Y),Y=X).
Note, you could also enter der(F1(X),X=X), which is valid, but confusing to the human because you have 2 X variables here, one used for derivation and one as a numerical value replacement!

Cyrille

Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP.
02-21-2018, 10:32 AM
Post: #7
 TheKaneB Member Posts: 175 Joined: Jul 2014
RE: How to calculate derivatives?
Hi Cyrille, thank you for the insight! Really appreciated

Software Failure: Guru Meditation

--
Antonio
IU2KIY
02-22-2018, 01:03 PM
Post: #8
 Aries Member Posts: 157 Joined: Oct 2014
RE: How to calculate derivatives?
(02-20-2018 11:16 AM)firedwheelman Wrote:  I am having a hard time figuring out how to calculate derivatives on the HP Prime. Do I need to download a certain program or can I compute it directly in CAS mode?

Yes, in CAS Mode, there is also a specific template
Best,

Aries :-)
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