Goal and scope
Find every component of X={a,b,c}, tau={empty,{a},{b,c},X}.
Use each induced topology, not a graph; do not extrapolate finite clopen components.
Main derivation
S01 · implies
Before
\{a\}\cap\{b,c\}=\varnothing,\quad\{a\}\cup\{b,c\}=XAfter
\tau\text{ is a topology}Conditions: none
Rule: topology · Uses: G1
Leaf basis: topology
Apart from the complementary pair, operations with empty and whole stay in the family; every union/intersection axiom follows.
S02 · definition
Before
\mathcal P(X)
After
\varnothing,\{a\},\{b\},\{c\},\{a,b\},\{a,c\},\{b,c\},XConditions: none
Rule: definition_here · Uses: G1
Leaf basis: definition_here
List all eight subsets before computing their induced topologies.
S03 · implies
Before
Y=\varnothing,\{a\},\{b\},\{c\}After
\tau_\varnothing=\{\varnothing\},\quad\tau_{\{p\}}=\{\varnothing,\{p\}\}Conditions: none
Rule: sets · Uses: S01, S02
Leaf basis: sets
The four small subsets have the listed induced topologies and no nontrivial separation.
S04 · implies
Before
Y=\{a,b\},\{a,c\}After
\tau_{\{a,b\}}=\mathcal P(\{a,b\}),\quad\tau_{\{a,c\}}=\mathcal P(\{a,c\})Conditions: none
Rule: sets · Uses: S01, S02
Leaf basis: sets
Ambient intersections give two-point discrete topologies, each separated by its two singletons and therefore disconnected.
S05 · implies
Before
Y=\{b,c\},\ XAfter
\tau_{\{b,c\}}=\{\varnothing,\{b,c\}\};\quad X=\{a\}\sqcup\{b,c\}Conditions: none
Rule: sets · Uses: S01, S02
Leaf basis: sets
The induced topology on {b,c} is indiscrete and connected; the two complementary nonempty opens explicitly separate X.
S06 · definition
Before
\mathcal C=\{\varnothing,\{a\},\{b\},\{c\},\{b,c\}\}After
C_a=\bigcup\{A\in\mathcal C:a\in A\}=\{a\};\quad C_b=C_c=\{b,c\}Conditions: none
Rule: definition_here · Uses: S03, S04, S05
Leaf basis: definition_here
Unite all connected subsets containing the given point, obtaining the unique inclusion-maximal candidates.
S07 · implies
Before
\{C_a,C_b\}=\{\{a\},\{b,c\}\}After
C_a\cap C_b=\varnothing,\quad C_a\cup C_b=X
Conditions: none
Rule: sets · Uses: S06
Leaf basis: sets
The distinct components are disjoint and cover the entire carrier.
S08 · implies
Before
X\setminus C_a=C_b\in\tau,\quad X\setminus C_b=C_a\in\tau
After
C_a,C_b\text{ both closed and open}Conditions: none
Rule: sets · Uses: G1, S07
Leaf basis: sets
Both components are closed and open in this finite model; this does not assert general components are open.