Lecture 12
Ch 2, part of sec 4 after thm 4.1, sec 6.
Define the notion of retract. Deduce that retracts give rise to
monomorphisms and epimorphisms of fundamantal groups. Define the notions of
defomation retract, contractible, and simply connected. State and prove the
Brower fixed point theorem.
Ideas: Give examples and non-examples of retracts, deformation retracts,
simply connected spaces, contractible spaces.