# What does this notation mean?

1. Sep 23, 2009

### BustedBreaks

u := -v

specifically the " := "

Here is the context. When f, g are suitably regular functions on R we can use the change of variable u:=-v etc..

I should add that I came across this in a Fourier Transform book..

Thanks!

Last edited: Sep 23, 2009
2. Sep 23, 2009

### Office_Shredder

Staff Emeritus
It usually means 'defined to be'.

So in this context, we know what v is, and we want to define u as a new variable. So you write u := -v to let the reader know u is being defined as -v (where v has been defined previously).

3. Sep 23, 2009

### BustedBreaks

Ah... well that makes sense
thank you very much.

4. Sep 24, 2009

### CRGreathouse

What, you haven't learned all half-dozen (dozen?) different symbols for "defined as" yet? :p

5. Sep 24, 2009

### EebamXela

the program MathCad uses the ":=" to define things like variables and functions. perhaps you saw a document made with mathcad?