# Problem Sheet P

This sheet is based on Lectures 36, 37, 38, and 39.

- Problem 1 considers the homology groups $H_n(M, M \setminus K ;R)$ when $M$ is
*not*$R$-orientable along $K$. - Problem 2 shows that for a manifold of dimension $n$, one can also obtain information about the torsion subgroup of $H_{n-1}(M, M \setminus K)$.
- Problem 3 asks to check that the cap product $ \frown$ really does descend to (co)homology.
- Problem 4 asks you to prove the homotopy axiom for Čech cohomology.
- Problem 5 asks you to prove
*Alexander Duality*. This is a massive generalisation of the Jordan-Brouwer Separation Theorem we proved in Lecture 17.

🤓 Feel free to ask a question if you are stuck! 🤓

Comments and questions?