Exercise 2: Tracing the MUX for sel=1, in0=1, in1=0 — Possible Solution ==================================================================== GIVEN ------------------------------ MUX formula: output = sel'.in0 + sel.in1 sel=1, in0=1, in1=0 STEP-BY-STEP TRACE ------------------------------ sel' = NOT(1) = 0 First term: sel'.in0 = 0.1 = 0 Second term: sel.in1 = 1.0 = 0 output = 0 + 0 = 0 RESULT ------------------------------ Output = 0, which correctly equals in1 (0) - exactly what should happen when sel=1 selects the second input. WHY in0 DOESN'T MATTER ONCE sel=1 ------------------------------ When sel=1, the first term (sel'.in0) always contains sel'=0 as a factor - and ANY value AND-ed with 0 is always 0, regardless of what in0 actually is (this chapter's own domination law: x.0=0). So the first term is forced to 0 no matter what in0 is, leaving the output entirely determined by the second term alone (sel.in1 = 1.in1 = in1) - which is precisely the intended MUX behavior: sel=1 should always select in1, completely independent of in0. WHY THIS WORKS AS AN ANSWER ------------------------------ Both terms of the MUX formula are computed explicitly rather than jumping straight to "sel=1 means in1," and the explanation for why in0 becomes irrelevant is grounded in a specific named Boolean law (domination: x.0=0) rather than just restated as "that's how a MUX works."