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# why does negative*negative=positive

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1. why does negative*negative=positive
2. "+"=2 lines
"-"=1 line
"-"+"-"=1 line + 1 line = 2 lines = "+"
3. (Original post by DanArthur)
"+"=2 lines
"-"=1 line
"-"+"-"=1 line + 1 line = 2 lines = "+"
lmao
4. You know, negative numbers were not widely accepted until the 18h century. Even then, they were contentious in some circles.

I dont know it but ill bet money that the explanation for this is something really obscure and complicated which probably involves complex numbers and trigonometry as well because thats just the way maths works.
5. (Original post by DanArthur)
"+"=2 lines
"-"=1 line
"-"+"-"=1 line + 1 line = 2 lines = "+"
This is probably the most logical explanation of that mathematical rule I have ever seen
6. Any complex number can be written in the form re^i(theta), for negative numbers theta = (2n+1)pi (r is the (positive) magnitude of the negative number)
When you multiply two numbers:
re^i(2n+1)pi*se^i(2m+1)pi = rse^i(2n+2m +2)pi = rse^i(2k)pi=
we know e^ik(2pi) = 1
therefore = rs*1 = rs
no negative sign any more (as r and s are both magnitudes (not 0 as we specified the original number is negative) and therefore positive).
7. Just imagine 1 dimension where negative is the reverse direction from zero, so by timesing you get --1 which is essentially reverse reverse 1
which would be 1.
8. (Original post by ValerieKR)
Any complex number can be written in the form re^i(theta), for negative numbers theta = (2n+1)pi (r is the (positive) magnitude of the negative number)
When you multiply two numbers:
re^i(2n+1)pi*se^i(2m+1)pi = rse^i(2n+2m +2)pi = rse^i(2k)pi=e^ik(2pi) = 1 therefore = rs*1 = rs
no negative sign any more
This makes my brain hurt. You're smart!
9. fml

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