[HP 35s] Finding the minimum of a FCN

07032015, 11:15 PM
(This post was last modified: 07042015 01:29 PM by Marcio.)
Post: #1




[HP 35s] Finding the minimum of a FCN
Hello all,
I've been trying to get the 35s to solve a program defined by a label but it just won't find any roots. Would anybody be kind enough as to take a look at my codes? This one calculates the derivative of a function using \(f'(x)=\frac{f(x+h)f(xh)}{2h}\) Code: LBL D This is the function being evaluated: Code: LBL F Basically, what I am trying to do is to find a local minimum by solving f'(x)=0, which in this case is 5/2. FN = D 3 SOLVE D. Very much appreciated. Marcio 

07042015, 08:21 AM
Post: #2




RE: [HP 35s] Finding the minimum of a FCN
Hi,
The Solver implicitly stores its guesses into variable D. So if you write "STO D", the guess will be overwritten by the current value of REGX. Try "RCL D" instead of "STO D". Best regards, Pascal 

07042015, 11:54 AM
(This post was last modified: 07042015 01:28 PM by Marcio.)
Post: #3




RE: [HP 35s] Finding the minimum of a FCN  
07042015, 04:40 PM
(This post was last modified: 07042015 05:03 PM by Dieter.)
Post: #4




RE: [HP 35s] Finding the minimum of a FCN
(07032015 11:15 PM)Marcio Wrote: Basically, what I am trying to do is to find a local minimum by solving f'(x)=0, which in this case is 5/2. You might be interested in another method of finding local extrema with a completely different approach. Take a look at this thread in the old forum, especially message #12. In your function be sure to replace x² with x*x since on the 35s the x² function does not work in the complex domain. Or use Horner's method: Code: LBL Y Set a suitable h: 1 E6 [STO] H Find the minimum between x=1 and 5: 1 [ENTER] 5 XEQ E [ENTER] SOLVING E= 2,5000 BTW, the program will also find the two roots on both sides of the minimum: 0 [ENTER] 2,5 XEQ Z [ENTER] SOLVING Z= 2,0000 2,5 [ENTER] 5 XEQ Z [ENTER] SOLVING Z= 3,0000 Dieter 

07042015, 04:48 PM
Post: #5




RE: [HP 35s] Finding the minimum of a FCN
Bookmarked!
It's really nice to have this option to solve and integrate programs on the 35s. Thanks Marcio 

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