I must cut a 2 inch pvc fixed drain from the disposal to the trap in order to clear it. How do I reattach it?

I assume your drains are 1 1/2" in size...

Buy 1 1/2" PVC coupling. After you are done with drain cleaning, connect the two pieces with coupling and glue.

Also, you may purchase 1 1/2" slip-on Fernco coupling. This coupling attaches with two s.s. bands.