Suppose that a complex \(X\) is the union of two subcomplexes \(A\) and \(B\) with \(A\), \(B\), and \(A \cap B\) contractible. Prove that \(X\) is contractible.
Question
Math 6520 • Algebraic Topology
Fall 2024 • Question 2
Question
Fall 2024 • Question 2
Suppose that a complex \(X\) is the union of two subcomplexes \(A\) and \(B\) with \(A\), \(B\), and \(A \cap B\) contractible. Prove that \(X\) is contractible.