GATE1988-12iia

Question

Using Armstrong’s axioms of functional dependency derive the following rules:

$\{ x \rightarrow y, \: x \rightarrow z \} = x \rightarrow yz$

(Note: $x \rightarrow y$ denotes $y$ is functionally dependenet on $x$, $z \subseteq y$ denotes $z$ is subset of $y$, and $\mid =$ means derives).