### Presidents, Masons, and National Treasure: Book of Secrets

 Part I Part II Part III Part IV Part V

One of my brothers sent me an interesting article that was recently published in the Washington Post:

Freemasonry, Eager to Step from Cultural Shadows

The informative, well written article relates among other things that the first scene of National Treasure: Book of Secrets was filmed in the grand auditorium of the George Washington Masonic Memorial in Alexandria, Virginia.

Besides George Washington, there is at least one other Masonic president featured in the movie: Theodore Roosevelt. Roosevelt's profile is featured prominently on Mount Rushmore of course. But, that's not Roosevelt's only connection to the National Park system. It turns out that his administration managed to set aside more than 42 million acres for national forests, parks, and wildlife refuges.

During a recent visit to the Grand Masonic Lodge of New York in Manhattan, one of the janitors showed me the desk where Roosevelt signed at least one of the documents that set aside this land. He said that Roosevelt liked to visit the lodge while in Manhattan to get away from the bustle of the city.

### Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

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The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems, there seem to be fewer explanations of the procedure for deriving the conversion, so here goes!

What do we actually want?

To convert the Cartesian nabla

to the nabla for another coordinate system, say… cylindrical coordinates.

What we’ll need:

1. The Cartesian Nabla:

2. A set of equations relating the Cartesian coordinates to cylindrical coordinates:

3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system:

How to do it:

Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables.

The chain rule can be used to convert a differe…

### Division: Distributing the Work

Our unschooling math comes in bits and pieces.  The oldest kid here, seven year-old No. 1 loves math problems, so math moves along pretty fast for her.  Here’s how she arrived at the distributive property recently.  Tldr; it came about only because she needed it.
“Give me a math problem!” No. 1 asked Mom-person.

“OK, what’s 18 divided by 2?  But, you’re going to have to do it as you walk.  You and Dad need to head out.”

And so, No. 1 and I found ourselves headed out on our mini-adventure with a new math problem to discuss.

One looked at the ceiling of the library lost in thought as we walked.  She glanced down at her fingers for a moment.  “Is it six?”

“I don’t know, let’s see,” I hedged.  “What’s two times six?  Is it eighteen?”

One looked at me hopefully heading back into her mental math.

I needed to visit the restroom before we left, so I hurried her calculation along.  “What’s two times five?”

I got a grin, and another look indicating she was thinking about that one.

I flashed eac…