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Topic: Keith Devlin's Online Course
Replies: 88   Last Post: Jan 5, 2014 9:31 PM

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Joe Niederberger

Posts: 3,279
Registered: 10/12/08
Re: Keith Devlin's Online Course
Posted: Dec 30, 2013 2:41 PM
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R Hansen says:
- -----------------------------------------------
It is consistency that tells us that a minus times a minus is a positive, because if it were not, mathematics would be inconsistent[1] and not deterministic.

<snip>

[1] Example of inconsistency

Given that 2 * 2 is 4 and assuming -2 * -2 is -4

a. Then 4 / 2 = 2 (if c = ab then a = c/b and b = c/a, arithmetic)
b. And -4 / -2 = -2 (same reason as above)
c. So far so good, and now we must decide what 2 * -2 is. 4 or -4?
d. If -2 * 2 is 4 then 4 / 2 = -2 (this is inconsistent with a)
e. If -2 * 2 is -4 then -4 / 2 = 2 (this is inconsistent with b)
- ---------------------------------------

More to the point -- your "proof" here isn't good enough.
In your parenthetical "reasons" you are essentially assuming the usual law of signs. That doesn't pass muster if your goal is to prove that no other law of signs is possible.

Cheers,
Joe N


Date Subject Author
12/24/13
Read Keith Devlin's Online Course
Robert Hansen
12/24/13
Read Re: Keith Devlin's Online Course
kirby urner
12/24/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/27/13
Read Re: Keith Devlin's Online Course
kirby urner
12/29/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/29/13
Read Re: Keith Devlin's Online Course
kirby urner
12/30/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/30/13
Read Re: Keith Devlin's Online Course
kirby urner
12/30/13
Read Re: Keith Devlin's Online Course
Robert Hansen
1/1/14
Read Re: Keith Devlin's Online Course
kirby urner
1/1/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/1/14
Read Re: Keith Devlin's Online Course
kirby urner
1/1/14
Read Why Casual Programming doesn't Exist
Robert Hansen
1/2/14
Read Re: Why Casual Programming doesn't Exist
kirby urner
1/2/14
Read Re: Why Casual Programming doesn't Exist
Robert Hansen
1/5/14
Read Re: Why Casual Programming doesn't Exist
kirby urner
1/5/14
Read Re: Why Casual Programming doesn't Exist
Robert Hansen
1/5/14
Read Re: Why Casual Programming doesn't Exist
kirby urner
1/5/14
Read Re: Why Casual Programming doesn't Exist
Robert Hansen
1/5/14
Read Re: Why Casual Programming doesn't Exist
Robert Hansen
1/5/14
Read Re: Why Casual Programming doesn't Exist
kirby urner
1/5/14
Read Re: Why Casual Programming doesn't Exist
Robert Hansen
1/5/14
Read Re: Why Casual Programming doesn't Exist
kirby urner
1/5/14
Read Re: Why Casual Programming doesn't Exist
Robert Hansen
12/26/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/29/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/28/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/28/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
kirby urner
12/29/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/29/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/29/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/29/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/29/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/30/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/29/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Anna Roys
12/29/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/29/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/30/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/31/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/30/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/31/13
Read Re: Keith Devlin's Online Course
Robert Hansen
12/30/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Robert Hansen
1/1/14
Read Re: Keith Devlin's Online Course
Anna Roys
1/2/14
Read Re: Keith Devlin's Online Course
Robert Hansen
12/30/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/30/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/31/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/31/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/31/13
Read Re: Keith Devlin's Online Course
GS Chandy
12/31/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/31/13
Read Re: Keith Devlin's Online Course
Joe Niederberger
12/31/13
Read Re: Keith Devlin's Online Course
Louis Talman
1/1/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/1/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/1/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/1/14
Read Re: Keith Devlin's Online Course
Louis Talman
1/1/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/1/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/1/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/2/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/2/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/2/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/2/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/2/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/2/14
Read Re: Keith Devlin's Online Course
Louis Talman
1/3/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/3/14
Read Re: Keith Devlin's Online Course
Louis Talman
1/2/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/2/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/2/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/2/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/3/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/3/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/3/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/3/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/3/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/4/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/4/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/4/14
Read Re: Keith Devlin's Online Course
Robert Hansen
1/5/14
Read Re: Keith Devlin's Online Course
GS Chandy
1/5/14
Read Re: Keith Devlin's Online Course
Bishop, Wayne
1/5/14
Read Re: Keith Devlin's Online Course
Robert Hansen

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