Fun With Sliceforms

I was recently inspired to make my first sliceform.

With a handful of index cards, a marker, and some scissors, I was able to make this fun representation of a surface in 3D!

Sliceform Front 1

Turn it to the side, and see the surface from a different perspective.

Sliceform Side

The inspiration was timely, as my Calculus class has been discussing cross-sections, traces, and level curves of surfaces in space.  What a perfect way to demonstrate how to understand a surface by looking at representative slices!

A great, simple tool, and you can see some examples of the sliceforms my students created, like the one seen below, here.

fun with sliceforms

Mathematical Quotations

This is a fun collection of mathematical quotations compiled by a professor at Trent University:

http://euclid.trentu.ca/math/sb/misc/quotes.html

The list includes some classics, such as the following famous remark from John von Neumann:

 “In mathematics, you never understand things; you just get used to them.

I also like this quote, attributed to Hungarian mathematician Raoul Bott:

“There are two ways to do great mathematics. The first way is to be smarter than everybody else. The second way is to be stupider than everybody else — but persistent.”

To add a favorite recent quote of mine to the list, a teacher was discussing how she used the idea of friendly numbers to help her quickly calculate in her head.  But while explaining the process, she warned us to be careful:  “Remember, what’s friendly to me may not be friendly to you!“.

Obvious, but Difficult

This is a fun conversation on MathOverlflow.net about famous examples of theorems in mathematics that are “obvious” but very difficult to prove.

http://mathoverflow.net/questions/51531/theorems-that-are-obvious-but-hard-to-prove

For example, the Jordan Curve Theorem essentially states that any closed curve in the plane divides the plane into an “inside” and an “outside”.  Obvious, right?  But very difficult to prove.

The Isoperimetric Theorem is another good example.  This theorem basically says that the most efficient way to surround area in the plane is with a circle.  Again, easier to believe than to prove.

And one of the responders notes that, after taking several hundred pages in their Principia Mathematica to prove that 1 + 1 = 2, Russell and Whitehead note that the proposition “is occasionally useful”.

“Obvious” is one of the most dangerous words in mathematics!

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