on my system all three of those commands are located in /usr/bin. make sure /usr/bin is in your PATH by typing:
if /usr/bin isn't there, edit your profile by appending /usr/bin to a line that looks like "PATH=$PATH:/sbin:/bin/"
and add "/usr/bin", so it looks like:
if you use the bash shell, your profile will be .bash_profile in your home directory. if you use ksh, your profile will be .profile in your home directory. if you use csh, god help you :-)
if the PATH variable isn't located in your profile files, try doing the same thing in ".bashrc" or ".kshrc".
if those commands aren't located in /usr/bin/, run a find to find where they are, and add those directories to your path:
find . -name "man" (or apropos, or whatis)
if that doesn't work, reply and we'll look into it further.
FYI: the root login often has a very minimal $PATH variable for security purposes. It wouldn't hurt to add /usr/bin (in my mind it'd be appropriate). Check it out to see if that's the problem.