Factor Principles/Conjunction on Left/Formulation 1

Theorem

 * $p \implies q \vdash \left({r \land p}\right) \implies \left ({r \land q}\right)$

Proof
It would, of course, be possible to derive the this rule from from Factor Principles: Conjunction on Right by applying the Rule of Commutation to the conjunctions on the RHS, but this is unnecessarily fiddly for a result so obvious. The Praeclarum Theorema does all the work we need instead.