yes because you just did
you use (a) if the next word is not a vowel. you us (an) if the next word is a vowel.
Example sentence - His pessimism wore on all of us.
Writing this sentence will make us more frendlier.
There is chaos among us.
The production helped us produce
moM ....UM...MERcy on us.
The boxer frighteningly barked at us.
Let us resolve our differences.
The band director strongly encourages us to use dynamics.
There's nobody home but us chickens. Let us go free!
I am using the word sortie in a sentence right now, but... You can use sortie as a verb or a noun: The general wanted us to sortie the opposing army.
the majestic view of palace thrilled us