where is libRmath.a & libRmath.so

R 2.7.2 -   the manual says 
configure
make

Which is what I did.  So I did read the manual and followed the directions. 
The manual is too terse to get me there.
  

You used the wrong tense.  In referring to R 2.7.2, only past tenses are 
grammatically correct.

If you want to say "the manual *is* too terse", then you need to install 
R 2.11.0.

Duncan Murdoch