draw one of the teeth of the gear.
select a radius size of the gear to be.
"array" the tooth.
when you type in "array" in the command line it will prompt you for several specifications.
you want to select polar array, it has a button for you to select a center point and it also asks you to specify the number of items you want to array and what degree to which you want to do this.
are you wanting to do this in 3d or 2d?