Having a notion of generalized sequences and their convergence is all very well as far as it goes. But the thing which made convergent sequences so useful to us was the rule for arithmetic of sequences that we developed in Chapter 3. All these arithmetic results for sequences have direct analogues for nets. We shall state a couple of them, and prove the most useful:
(For the proof, just apply Lemma 8.7 to the upper and lower Riemann sums.)