A few reflexions on the function app

[DegrangeM]

• Extremum are local extremum. The app will ignore global extremum. For example the function x³-x will only display the maximum at 1/√3 and not for exemple the one for x=2 (this is true even if we set the function de be defined at [-2;2]). Maybe it should also display the global extremum ? Even if they are most of the time not interesting, it will be better mathematically.
• If there is multiple local maximum, the app will allow to cycle through all of them. Maybe in the calculate menu the term "Maximum" should be in plural "Maximums" ?
• The calculate menu can be a little tricky if you don't know it's rules. It only search for x between the x axis range. A student could want to search a local maximum, an antecedent and got wrong result because the solution is outside the x axis (the student could think the calculator will search everywhere independently of view range). However this does not apply for y axis range, if the solution is outside vertical displayed axis, the calculator will move the view range to display the solution.
  • Maybe display somewhere that the search will be limited on the x axis ? This might confuse some started learner though
  • Maybe try to search for all range ? Might be difficult and computation intensive and it will probably miss things for strange function
  • I don't think there is really good solution but the current state bother me a little

[Stephan-P]

As with all other non-CAS graphical calculators, calculations on graphs are only done within the visible part of the graph. If a point of interest, be it a max, min, zero or intersection, is not within view then the calculator will not find it for you. Calculation of such points of interest is also performed by 'approximation' and generally via some form of 'sign change'. Because of this, a min or max that is located right on the edge of the visible area of the graph may not be (cannot) found.

These are two - one could say - 'non-mathematical' essentials of graphical calculators. They don't perform math on graphs, they approximate line crossings and sign changes.

Further, I suspect an error in your given function f(x) =x^3 - x as I can find no point of interest at x=2.

[DegrangeM]

As with all other non-CAS graphical calculators, calculations on graphs are only done within the visible part of the graph.

So maybe it should be written somewhere.

Further, I suspect an error in your given function f(x) =x^3 - x as I can find no point of interest at x=2.

In my example, the function is defined on [-2;2] so there is a maximum in 2.