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Topic: In "square root of -1", should we say "minus 1" or "negative 1"?
Replies: 5   Last Post: Dec 3, 2012 12:53 AM

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Robert Hansen

Posts: 7,809
From: Florida
Registered: 6/22/09
Re: In "square root of -1", should we say "minus 1" or "negative 1"?
Posted: Dec 2, 2012 8:39 AM
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On Dec 2, 2012, at 1:19 AM, kirby urner <kirby.urner@gmail.com> wrote:

> Yes, though mostly just in passing.

Might you have that backwards? Wouldn't mentioning topics without any development, be "in passing"?

In any event, isn't most of the story telling for the teacher to do? I would shore up a few of the stories in the book, add some plot development, but the majority of the book's job (75%) remains the technical development and exercises. The trick is how to do all of that and not end up with students later asking "Which latitude is negative? North or South?" My point being you want application of the math (modeling), not rote association.

There is a lot of fluency issues to be dealt with here. Some even worse than "a minus times a minus", like what happens to the expression "x > y" when you multiply each side by (-1)? Or how about expressions involving "absolute value"? Remember those? Does anyone like absolute value?


On Dec 2, 2012, at 1:19 AM, kirby urner <kirby.urner@gmail.com> wrote:

> Note that reading "-5" as "minus five" and not "negative five" is
> explicitly encouraged. Page 106.


Interesting. Dolciani fixes this in the 1965 book. Scroll to the end (Page 112 ended up at the end)...

https://www.dropbox.com/sh/hz6q14yeafltfmn/_Y8FmVMapj/Dolciani-1965.pdf


> No turtle graphics yet :-)

Ha, no. But these were the textbooks used by the students that invented logo and turtle graphics.


Bob Hansen



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