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Jun 17, 2020 at 7:59 comment added user43326 OK, it wasn't really Kunneth, but the thing is $H^*(F.Z/2)$ is a (graded) vector space over $Z/2$, so taking cohomology with $H^*(F.Z/2)$ coefficients is same as taking cohomology with $Z/2$-coefficients and then tensoring with $H^*(F.Z/2)$.
Jun 17, 2020 at 6:48 comment added user101010 @user43326 What do you mean by using the Kuenneth here? The only Kuennth that comes to mind for me here is for computing (co)homology of products. The reason these classes are drawn is not really because they hit the bottom (see the next spectral sequence that is pictured in that section), but because they are involved in the computation of the cohomology of the total space through degree 8.
Jun 16, 2020 at 19:10 comment added user43326 As to your first question, since we are talking about the mod 2 cohomology, we can simply use the Kunneth to fill in. The reason why Hatcher bothered to mark these classes is, presumably, becaute they hit the claas in the bottom line.
Jun 16, 2020 at 17:33 history edited Arun Debray
added {spectral-sequences} tag
Jun 16, 2020 at 16:09 history asked user101010 CC BY-SA 4.0