Wednesday, February 11, 2009

Finding Points of Intersection with The Geometer's Sketchpad

So Frank asked me about finding intersections of plotted linear functions at our Web 2.0 session last week. It turns out that constructing the intersection of two lines is trivial but of two function plots is not.

I told him the story about how happy I was to have written a custom tool to take two linear functions as input and create their point of intersection for Stephanie. The .gsp file is here.

At least, I was happy until I asked my pal Shawn Godin about it and he very quickly created a sketch that takes two polynomial functions (and maybe other kinds), and the origin and plots the functions, creates a locus of all the points of intersection found using Newton's Method, and labels one of them. You can then drag the point on the locus through all the points of intersection. His .gsp file is here.

Guess which one of us is working on our PhD in Mathematics?

Thanks Shawn for giving me permission to share the sketch. I'll be curious to see if this post gets as much traffic as the post about graphing inequations in Sketchpad, which also reported Shawn's guru status in the Sketchpad community.

3 comments:

Jan said...

Hello, Roos!
I met with your interesting developments. Thank you! I am a teacher of mathematics, interested in GSP. I have a blog about this topic: http://janka-x.livejournal.com/. If you want, then they can download my files. I am from Belarus. Sorry for my English.
Have a good time,
Jan.

Ross Isenegger said...

Hi Jan,

Thank you for sharing your compelling looking site. The illustrations are very attractive - if only I could read the text.

Ross

Ross Isenegger said...

Finding points of intersections of function plots (as well as of loci) and tons of other neat new features are now in version 5 of Sketchpad.