## Search found 844 matches

- Fri Sep 11, 2015 5:19 am
- Forum: Logic and Philosophy of Mathematics
- Topic: Proving that the difference between any two anagram numbers is always a multiple of nine
- Replies:
**59** - Views:
**6081**

### Re: Proving that the difference between any two anagram numbers is always a multiple of nine

Here's the proof that the difference of anagrams is divisible by 9. First, note that x = x0 + x1 * 10 + x2 * 10^2 + ... + xn * 10^n (writing xn or sometimes x_n to mean "x_subscript_n") and likewise y = y0 + y1 * 10 + y2 * 10^2 + ... + yn * 10^n. Note that since the x_i's are just a rearrangement of...

- Thu Sep 10, 2015 12:22 am
- Forum: Logic and Philosophy of Mathematics
- Topic: Is infinity all black and white?
- Replies:
**5** - Views:
**1126**

### Re: Is infinity all black and white?

@PhilX, I resurrected this months-old thread because you have a lot of similar questions about transfinite cardinals in this and other threads and I wanted to unpack some of these issues if you're still interested. The question of whether every infinite set is cardinally equivalent to an Aleph is ac...

- Tue Sep 08, 2015 11:54 pm
- Forum: Logic and Philosophy of Mathematics
- Topic: Differential calculus defined by differences - what more meaningful ?
- Replies:
**12** - Views:
**1496**

### Re: Differential calculus defined by differences - what more meaningful ?

A quick Google search will show that this author is a well-known crank. Regarding calculus, he clearly has never seen the proper formalization of the concept of a limit. He has an Amazon book if anyone wants to send him money.

- Tue Sep 08, 2015 11:43 pm
- Forum: Logic and Philosophy of Mathematics
- Topic: Does the center of a disk exist?
- Replies:
**22** - Views:
**3259**

### Re: Does the center of a disk exist?

a) Case of a physical disk. You can't precisely find or define the center to arbitrary precision because of measurement error. And any physical rotational mechanism is imperfect and has some amount of wobble. So there is no stationary point in a physical spinning disk. b) Case of a mathematical disk...