The Museum of HP Calculators

HP Forum Archive 21

 Extremums on PrimeMessage #1 Posted by Richard Berler on 12 Oct 2013, 6:58 p.m. I just discovered how to quickly find extremums of a function...I enter function in functions app (make sure you check mark it, and de check other functions) copy the function, go back to home and get zeros from cat, call up d?/dx from entry template key, paste in the function that I just copied, and hit enter. This gives me potential extremums. Then, go to setup plot, and put in an x range that is fairly tightly centered on a zero, hit view, hit auto scale, and the graph comes up, touch screen near extremum, go to menu, function, extremum! Quick and easy! This shows how outstanding the graphing capability on this unit is...nice!

 Re: Extremums on PrimeMessage #2 Posted by Tim Wessman on 13 Oct 2013, 10:29 a.m.,in response to message #1 by Richard Berler Maybe I'm missing something, but why can't the process just be: enter your function (check/uncheck), plot, press fcn->extremum, autoscale. Seems that does what you are looking for without all the extra steps. Press ENTER to start the marching cursor. Also, you can use your F directly. In the cas screen: zeros(d(F1(x))/dx) or if preferred, zeros(F1(x)') does the same. TW Edited: 13 Oct 2013, 10:29 a.m.

 Re: Extremums on PrimeMessage #3 Posted by Richard Berler on 13 Oct 2013, 1:21 p.m.,in response to message #2 by Tim Wessman A function such as (x^2*(x+1)^3)/((x-2)^2 * (x-4)^4) has a graph that is close to zero except for inf at x=2 & x=4, and a min at about x=2.47 of about 211. I don't understand how to march through the possible extremums in the way you suggested. By manually entering a tight range about potential extremums and using auto scale, I get a nice plot centered on my point of interest, and can then call for the extremum. This seems particularly handy where an initial graph is flat so as to not suggest extremums exist or how many... Clearly, I'm not understanding this (though my work around really shows the utility of the graphing capability interfacing with the home screen). I think this also speaks to a real need for a physical manual for a capable, complex tool such as the Prime...they were of such value for even recent offerings such as the 35s and the 15c LE! I can't imagine students, let alone their teachers taking as full advantage of this device without a physical manual...you can see all the questions appearing on this forum from folks that are highly experienced in this area...I wonder how perplexed a more general audience of folks that you hope to purchase this unit will be. In any case, thanks for bringing this product into being, and I hope that HP will attach importance to this product offering/market.

Go back to the main exhibit hall