# Freehand Shape as input for custom tools

mikkelstouby shared this idea 7 years ago

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

1

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?

1

It seems you have forgotten an attachment.

1

Thanks :)

Here's a preview of the real thing:

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

1

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.

1

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

1

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.