Finding Min/Max of a function for HP67

05222016, 07:34 PM
(This post was last modified: 05222016 07:36 PM by Dieter.)
Post: #10




RE: Finding Min/Max of a function for HP67
(05222016 01:26 AM)PedroLeiva Wrote: It's more complicated than I imagined. Luckily I made the query. Hmmm... honestly, I do not quite understand the problem. You simply enter f(x) as a short routine just as you do with any other "classic" HP, be it the 65, the 41, the 67/97 or most others. The argument x can be expected in the Xregister, so you simply type what you'd also do in a manual calculation. In this example f(x) is e^{x}–3x², so it's [e^{x}] [LstX] [x²] [3] [x] [–]. This is what you enter at LBL E so that f(x) can be calculated by a simple [E] or GSB E. Checking for a minimum or maximum is easily done by RCL 3 after the program has finished. If the result is positive it's a minimum, and if it's negative there's a maximum. A value of (or very close to) zero would indicate a possible inflection point, but this should not happen as the program divides by R3 so that it would have stopped with an error before. You could add these lines: Code: ... ... This calculates –sign(f"(x)). So after the program has finished, a simple X<>Y will show –1 (minimum) or +1 (maximum). Dieter 

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