proof of limit rule of product
Let and be real (http://planetmath.org/RealFunction) or complex functions having the limits
Then also the limit exists and equals .
Proof. Let be any positive number. The assumptions imply the existence of the positive numbers such that
(1) |
(2) |
(3) |
According to the condition (3) we see that
Supposing then that and using (1) and (2) we obtain
This settles the proof.