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Dragonfall
Sep18-08, 12:11 PM
Does the said function satisfy:

(1)continuity
(2)never constant
(3)has uncountably many zeroes

1 and 3 is trivial, but I'm not sure about 2.

Dragonfall
Sep22-08, 12:56 PM
Hello hello

CRGreathouse
Sep22-08, 02:43 PM
I'm not sure how you'd even define the distance, given that every point in (0, 1) has a point in the Cantor set within epsilon for any epsilon > 0.

Moo Of Doom
Sep22-08, 05:19 PM
I'm not sure how you'd even define the distance, given that every point in (0, 1) has a point in the Cantor set within epsilon for any epsilon > 0.

Not true. The Cantor set is not dense in (0, 1). For example the point 1/2 is at least 1/6 away from any point in the Cantor (middle-thirds) set. In fact, dist({1/2}, CantorSet} = 1/6.

CRGreathouse
Sep23-08, 01:15 AM
Ah... clearly I was thinking of something else. That'll teach me to post late at night!

Doodle Bob
Sep23-08, 05:30 AM
Does the said function satisfy:

(1)continuity
(2)never constant
(3)has uncountably many zeroes

1 and 3 is trivial, but I'm not sure about 2.

If x=1/2, then the distance from x to the Cantor middle-third set would be 1/6. If x=0, then the distance would be 0. Hence "not constant".

I find the the use of the word "never" strange since it sounds to be like asserting otherwise the function would be constant on, say, the Tuesdays after a new moon, but not constant all other days.

Possibly what you mean is that there are no open sets on which the function is constant.

Dragonfall
Sep24-08, 01:28 AM
By "never" I mean that there is no interval on which it is constant.

This is was a problem I thought up. My intuition was that since if a function is "continuous", and "never constant", each time you hit a zero you must "wave" up and down in order to hit a zero again. So this will make the number of zeros "countable". But the distance function from x to the cantor set seems to be "continuous and never constant" but has uncountably many zeros.