How to include math operation?

[Matteo]

Hi 
I would like to use some math function but the compiler says always to me ;
undefined reference.. 
so I try to add in the makefile -lm where there are specificated the LIBS like
following;

LIBS = -lm -lrtemsall -lc

but the result it's the same, How I have to do?
Someone can help me .
I have configured rtems for i386 and pc386.

Thanks in advantage 
Matteo Posterli