At the REPL, type:
(in-package :fast-math)
Then type (f* 10d0 30d0).
That didn't fix it, but the problem was related; when I evaluated the defmacro commands in a secondary buffer, it didn't have (in-package :fast-math) at the top, so the macros were installed in cl-user. Of course, when in the fast-math package at the REPL, the commands weren't available! I forgot that slime plays that package magic---thanks for the tip!
Will