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Sylow of a group

  1. Apr 1, 2012 #1
    Let G be a finite group, H and K subgroups of G such that G=HK. Show that there exists a p-Sylow subgroup P of G such that P=(P∩H)(P∩K).

    I found this proof and it is clear http://math.stackexchange.com/questions/42495/sylow-subgroups but I do not understand step 3 which is "It is clear in this situation that P=(P∩H)(P∩K)". Help.
    Last edited: Apr 1, 2012
  2. jcsd
  3. Apr 1, 2012 #2

    Well, after part (3) in the stackexchange there's a further poster who also had a problem with this step, and I think it isn't THAT clear, as the other guy wrote, that P = (P/\H)(P/\K)...
    The same question as that further poster asked came to my mind: is normality something we can do without?

    It'd be interesting to know where did you find this problem.

  4. Apr 1, 2012 #3
    It is in Finite Group Theory I. Martin Isaacs page 18
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