3 ms·
summary: -1*-1 = -1*-1 + -1*1 + 1 = -1*(-1 + 1) + 1 = -1*0 + 1 = 1
by tromp 7y ago
summary:
-1*-1 =
-1*-1 + -1*1 + 1 =
-1*(-1 + 1) + 1 =
-1*0 + 1 =
1
- deleted 7y ago[deleted]
- mathnmusic 7y agoThe explanation that appeals to me: If number N is an arrow on the number line from 0 to N, then multiplying N by -1 flips the arrow with the result -N. Multiplying by -1 again would be another flip, taking you back to N. So a flip followed by a flip is same as no change (i.e. multiplicative identity 1).
- mantap 7y agoThis would be clearer if the -1 was in parentheses (I can't do it because I'm on mobile). I think you are missing a plus sign on line two.
- nabla9 7y agoin complex plane you can go e^[i(2nπ+π)] × e^[i(2nπ+π)] = ... e^[2i(2πn+π)] = 1