00:01
Okay, so let's get started with part a of our exercise.
00:06
Well, we are going to show that k is discrete, and how can we do this? well, let's consider a point x belonging to k.
00:17
Then we are going to find a positive integer, such that x is equal to 1 over n.
00:28
Now here we are going to go over two cases.
00:33
Case 1, n greater than 1.
00:39
If n is greater than 1, then we fix epsilon, which is going to be 1ā2, multiplied by the minimum between the distance of x and 1 over n minus 1, and x this one is minus okay and here we are going to have the distance between x and 1 over n plus 1 okay perfect well at this point is clear that the ball with radius epsilon and center x intersection with k is equal to x only so basically we did this we had x here here we had one over okay this one is n minus one this one is one over n plus one and we just found a ball with radius epsilon such that the intersection of this ball with k is x only so it was easy.
02:03
Now case two well case two if n is equal to 1 so n equal to 1 then basically we're going to do the same thing but this time epsilon is going to be one half multiplied by the minimum between, oh actually now we don't need the minimum, we just need to consider the distance between x and one half, even easier...