### Poetry at the Goat and Superhero Outfit Changes

This place is so cool!

I was sitting at the Hungry Goat tonight working on another tech book during the weekly poetry reading. I'm not sure if that's a cognitive dissonance or an oxymoron, but that's what I was doing. Actually it's probably neither, but I've always wanted to use the word dissonance.

Anyway! I was sitting at the front door working away. OK, I wasn't working. The trial version of Microsoft Office had expired and I was installing the new version, which was taking forever, so, umm... yeah... I was actually doing what I do best down here: watching the world go by.

So, getting back to the story, as I'm watching the world go by, (accompanied by ranting poetry in the background), a woman pulls up on a classic Vespa and parks on the sidewalk. She's got a bob haircut, and she's wearing a white leather jacket, pink tights, and a pair of white go-go boots. For all the world, she looked like she was going to do an interpretive dance to one of the poems. I smiled and got back to my very intense installation work, (watching the little green bar go across the screen).

About two minutes later, she comes back out. Except now, she's wearing heels, a sleek dress, and the white leather jacket. Apparently, the Goat is her Boulder phone booth. She laid the boots on the floor of the Vespa, (conclusively proving that yes, there is no crime in Boulder), and off she went to whatever it is you can do down the street with a nice dress, but not with pink tights.

Always something new here. And to think, I almost bought a TV!

### 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…

### The Javascript Google URL Shortener Client API

I was working with the Google API Javascript Client this week to shorten the URLs of Google static maps generated by my ham radio QSL mapper. The client interface provided by Google is very useful. It took me a while to work through some of the less clear documentation, so I thought I'd add a few notes that would have helped me here. First, you only need to authenticate your application to the url shortener application if you want to track statistics on your shortened urls. If you just want the shortened URL, you don't need to worry about this. The worst part for me was that the smaple code only showed how to get a long url from an already shortened rul. If you follow the doucmentaiotn on the insert method, (the method for getting a shortened url from a long one), there is a reference to a rather nebulous Url resource required argument. It's not at all clear how to create one of these in Javascript. The following example code shows how:
var request = gapi.clie…