Exercise · ZW-PATH-CONNECTED-SPACE-007 · ★★☆ Intermediate
Which of these subsets of \(\mathbb R^2\) is path-connected?
Choose one option.
Show answer
- D. the unit circle
Explanation
The circle is traversed by an arc between any two of its points. The others have several separate pieces: two disks, four quadrants or isolated points.
Review the concept: Path-connected space
A space \(X\) is path-connected if every pair of points \(a,b\in X\) is joined by a path: a continuous function \(\gamma:[0,1]\to X\) with \(\gamma(0)=a\) and \(\gamma(1)=b\).
\[\forall a,b\in X\ \exists\,\gamma:[0,1]\to X\text{ continuous},\ \gamma(0)=a,\ \gamma(1)=b\]
More practice problems: path-connected space
- ZW-PATH-CONNECTED-SPACE-001 Which of these subsets of mathbb R is path-connected?
- ZW-PATH-CONNECTED-SPACE-002 Which is a path in mathbb R from 2 to 5?
- ZW-PATH-CONNECTED-SPACE-003 Is the space X=\1,2,3\ with the indiscrete topology path-connected?
- ZW-PATH-CONNECTED-SPACE-004 Why is \1,2\ with the discrete topology not path-connected?
- ZW-PATH-CONNECTED-SPACE-005 One of these topologies on X=\1,2,3\ does not make X path-connected. Which one?
- ZW-PATH-CONNECTED-SPACE-006 Which statement is true?
- ZW-PATH-CONNECTED-SPACE-008 If α joins a to b and β joins b to c, which path joins a to c?
- ZW-PATH-CONNECTED-SPACE-009 How many of the 29 topologies on a 3-point set make it path-connected?