It is easy to see why a straight line supply function going through the origin is unit elastic.
And here is a numerical example with some plots.
It is easy to see why a straight line supply function going through the origin is unit elastic.
And here is a numerical example with some plots.
If you are interested in applications of (cross-price) elasticities you may want to read pages 23-27 of this document.
This is from the Nutrasweet antitrust case.