Hasse Diagram Divisibility
1. **State the problem:**
We are asked to draw the Hasse diagram for the partial order defined by the divisibility relation $a \mid b$ on the set $\{1, 2, 3, 4, 6, 8, 12\}$.
2. **Understand the relation $a \mid b$:**
This means $a$ divides $b$ without remainder. For example, $1$ divides all elements, $2$ divides $4, 6, 8, 12$ etc.
3. **Find covering relations:**
In a Hasse diagram, we draw edges representing the "covering" relation, meaning $a \mid b$ and there is no $c$ such that $a \mid c \mid b$ with $c \neq a, b$.
- From $1$, the elements covered immediately are $2$ and $3$ because they are the smallest multiples in the set.
- $2$ covers $4$ and $6$ (since $2 \mid 4$ and $2 \mid 6$, and no intermediate divisor in the set between $2$ and $4$ or $6$).
- $3$ covers $6$.
- $4$ covers $8$ and $12$.
- $6$ covers $12$.
- $8$ and $12$ are maximal elements.
4. **Visual structure:**
- Bottom level: $1$
- Second level: $2, 3$
- Third level: $4, 6$
- Top level: $8, 12$
5. **Interpretation:**
Edges go upward from smaller divisor to larger multiple without intermediate elements.
**Final description:**
- $1 \to 2$, $1 \to 3$
- $2 \to 4$, $2 \to 6$
- $3 \to 6$
- $4 \to 8$, $4 \to 12$
- $6 \to 12$
This pictorially arranges nodes so that larger multiples are placed higher, clearly representing the partial order by divisibility.
Thus the Hasse diagram corresponds exactly to the described relations.