# Homology of RP(2)

1. Dec 25, 2007

### Sephi

I'm currently learning some homology theory but I have some difficulties computing homology groups of a few simple spaces. If someone could do the explicit calculation for RP(2), it would be really nice.

Thank you :)

2. Dec 25, 2007

### mathwonk

the universal covering space is the 2 sphere, so pi 1 is Z/2Z, hence also the first homology group. that does it since the space is connected non orientable manifold so the zeroth homology is Z and the second homology i guess is zero.

i am just recalling this from 40 years ago since they don't let me teach topology for some reason, so i could be wrong.

3. Dec 25, 2007

### mathwonk

another approach is to represent RP^2 as a circle with a disc attached by a map of degree 2. then there is a little formula for the homology groups, in the chapter on cell complexes.