Let Δ, ∇ ∈{∧, } be such that ( p → q ) Δ( p ∇ q ) is a tautology. Then

Let $\displaystyle \Delta, \nabla \in\{\wedge, \vee\}$ be such that $\displaystyle (\mathrm{p} \rightarrow \mathrm{q}) \Delta(\mathrm{p} \nabla \mathrm{q})$ is a tautology. Then