Wednesday, 3 August 2016

elementary set theory - Set of continuous functions from mathbbR to mathbbR is equinumerous to mathbbR



I am trying to prove that the set C:={ffRRf is continuous} is equinumerous to R.




To achieve this, I note that an fC is ''pinned down'' by Q, i.e. if I know how f behaves on Q, I know all of f, since Q is dense in R and f is continuous. So there is an easy injection from C to {ffRQf is continuous}.



The latter set can be embedded into RN, but I'm afraid that fact won't help me, since (as I believe): not RNR.



Could someone hint me into the right direction on proving CR (via CR)?


Answer



You have |RN|=|(2N)N|=|2N×N|=|2N|=|R|


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