Explains it nicely. I can not improve on it.
In mathematics, you don't understand things. You just get used to them.
I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.
Yep, another nice page.
It might be worth mentioning that an "outward facing" square bracket is sometimes used instead of a round one for open intervals.
eg. (0,1) = ]0,1[
() is my preferred notation though.
Why did the vector cross the road?
It wanted to be normal.