How to test if a given path is a mount point

I discover that on my Fedora 7 there is a mountpoint command.

From man mountpoint:

NAME
       mountpoint - see if a directory is a mountpoint

SYNOPSIS
       /bin/mountpoint [-q] [-d] /path/to/directory
       /bin/mountpoint -x /dev/device

Apparently it come with the sysvinit package, I don't know if this command is available on other systems.

[root@myhost~]# rpm -qf $(which mountpoint)
sysvinit-2.86-17

if mount | cut -d ' ' -f 3 | grep '^/mnt/disk$' > /dev/null ; then
   ...
fi

EDIT: Used Bombe's idea to use cut.