Function - Find root
01-07-2022, 05:44 AM
Post: #11
 jte Member Posts: 264 Joined: Feb 2014
RE: Function - Find root
(10-15-2021 02:23 PM)StephanP Wrote:  Only when the cursor is at a slope wherein the root lies, it is actually properly found.
This helps me understanding the underlying algorithm and also helps my explaining things to my students.
But it still feels strange to me that when i issue a command Find root, that the calculator chooses to give me an extreme as a result. That’s confusing to me and for sure for students who are trying to figure out how to work with a graphic calculator.
Things could be made more clear, e.g. by simply saying: No root found!

There certainly are a few possible improvements that could be made here.

I, too, was surprised by the 39gs’s behaviour when I first encountered it (while implementing the Function app for the 39gII). While it may be obvious to us that a reported extrema is not a root, the root finding routine is unaware of the vertical scale of the plot. Where a root may exist if real arithmetic is used for evaluation, there may only be nearby extrema when floating-point arithmetic is used for evaluation. (Just a bit earlier, I gave the example of F1(X)=SIN(X)^2; there will generally be local non-zero minima near non-zero integer multiples of π for this function when viewed through a floating-point lens.)
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 Messages In This Thread Function - Find root - StephanP - 10-15-2021, 12:01 PM RE: Function - Find root - Arno K - 10-15-2021, 02:03 PM RE: Function - Find root - StephanP - 10-15-2021, 02:13 PM RE: Function - Find root - StephanP - 10-15-2021, 02:23 PM RE: Function - Find root - Albert Chan - 10-16-2021, 01:59 PM RE: Function - Find root - Wes Loewer - 10-17-2021, 03:34 AM RE: Function - Find root - jte - 01-07-2022, 05:32 AM RE: Function - Find root - jte - 01-07-2022 05:44 AM RE: Function - Find root - Arno K - 10-15-2021, 03:20 PM RE: Function - Find root - Wes Loewer - 10-16-2021, 01:31 PM RE: Function - Find root - jte - 01-07-2022, 03:38 AM RE: Function - Find root - ObiWanKenobi - 01-10-2022, 02:49 PM

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