Extremums on Graph
01-25-2020, 04:21 AM
Post: #1
 lrdheat Senior Member Posts: 583 Joined: Feb 2014
Extremums on Graph
Curious as to why some functions in the graphing app will not find an extremum, even though one is found in solve in the CAS environment. The 2nd derivative of (e^2*x)*sin(3*x) is an example.
01-25-2020, 01:33 PM
Post: #2
 roadrunner Senior Member Posts: 306 Joined: Jun 2015
RE: Extremums on Graph
Assuming you are talking about the advanced graphing app, I had no trouble finding extremum. Just select from the menu: Trace/Poi/Vertical Extrema, then touch on the plot near the extrema you want.

01-25-2020, 03:09 PM
Post: #3
 lrdheat Senior Member Posts: 583 Joined: Feb 2014
RE: Extremums on Graph
I was in regular function graphing app...
01-25-2020, 06:13 PM
Post: #4
 Carsen Member Posts: 200 Joined: Jan 2017
RE: Extremums on Graph
I was able to find multiple extremums on the 2nd derivative of (e^2*x)*sin(3*x) in the Function App. Everything worked as expected. The 2nd derivative was solved in the HOME environment in RPN mode & put in the Function app. Then plotted.

I used my G1 HP Prime with the 20181016 firmware (not the latest).

We may need to provide further details in order to figure out what's going on.
01-25-2020, 09:52 PM
Post: #5
 lrdheat Senior Member Posts: 583 Joined: Feb 2014
RE: Extremums on Graph
What is odd is that I can put the function in regular graph app in, say, F1(X), and d(d(F1(X))) in F2(X), and it plots. Finds roots but not extremums. I canâ€™t seem to get the same procedure to work in advanced graph app.
01-26-2020, 09:22 PM
Post: #6
 Carsen Member Posts: 200 Joined: Jan 2017
RE: Extremums on Graph
Ahhh. I get it. You used the derivative template to calculate the 2nd derivative of (e^2*x)*sin(3*x) in the function app itself. When I did that, I was able to replicate your example.

Good question. Unfortunately, I don't know why it behaves this way.
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