Freehand Shape as input for custom tools

mikkelstouby shared this idea 7 years ago
Answered

I know this might not be so easy to implement but it would increase the value of freehand shapes a lot if the functions created this way could be used as input for a custom tool.


An example of the use of this:

As a teacher I often want to have a function that "goes something like this". The freehand shapes are almost perfect for this. It is a huge disadvantage though that the tangent tool does not work for this kind of functions. To overcome this I do one of two things:


Create a function (f) with the freehand tool

Create a point (A) on f

g(x)=Polynomial[A,(x(A)-0.1,f(x(A)-0.1)),(x(A)+0.1,f(x(A)+0.1))] (this is rough of course but it is all I need)

Tangent[A,g].


OR


Create a function (f) with the freehand tool

g(x)=FitPoly[f,5] (this is very often enough)

Create point (A) on g

Tangent[A,g].


The problem is that this is a bit cumbersome in class and a custom tool would be great.


Best regards,

Mikkel

Comments (6)

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Nice idea, we could just implement (approx) tangents for Freehand Functions for you :)


Here's a mockup of what it would look like - do the values of the sliders give a nice result for the sort of functions you would use?

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It seems you have forgotten an attachment.

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Thanks :)

http://tube.geogebra.org/st...


Here's a preview of the real thing:

http://tube.geogebra.org/st...

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First of all, thanks a lot for looking into this.


"The real thing" looks great and personally I would mostly use this for rather smooth functions so this will be perfect.


Regarding the values of the sliders I think there is some kind of bug when the order is set to 3 or 4. At least the tangent is not very close to the point A.

Generally I think one should avoid using more points than order+1 (including A) because otherwise the tangent won't pass through A and that will look stupid. For my purpose I don't think it will be necessary to use polynomials of higher degree than 5.


As I said this is great work but I still think it could be useful in general to be able to use freehand functions in a custom tool.

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ps just added a Toolbar so you can try it out for different functions (use the Freehand Tool then the Tangent Tool) :)

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As far as I can tell it works great. At least it does what I need. Typically I would just draw something that looks like a polynomial of degree 3-5 meaning "some function" so I don't need anything fancier than this. Weird functions doesn't do well on smartboards anyway.

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