Concerning $m_1m_2=-1$
140717
Explain why perpendicular lines have negative reciprocal slopes
126586
Change of basis matrix for $B_2\{(1,-1,0),(1,0,-1)\}$ to $B_1\{(0,1,-1),(1,1,-2)\}$
134450
Chinese Remainder Theorem $\ x\equiv m_k-2\pmod{m_k}$
146093
Why if $n \mid m$, then $(a^n-1) \mid (a^m-1)$?
110826
prove that : $ i = \sqrt {-1}\ $
78471
Closure of $\{\frac{1}{n}\}:=M$
81875
why is $\sqrt{-1} = i$ and not $\pm i$?
78736
Check my proof that $(ab)^{-1} = b^{-1} a^{-1}$
95057
Possible fake proof of $1= -1$
34430
Why does $(\frac{p-1}{2}!)^2 = (-1)^{\frac{p+1}{2}}$ mod $p$?
111515
Proving that $-a=(-1)\cdot a$
87848
Formal proof for $(-1) \times (-1) = 1$
39908
Finding the error in this proof that 1=2
70266
1-1 correspondence between [0,1] and [0,1)
34929
Prove ${M}\choose{N_1}$ ${M}\choose{N_2}$ $\leq$ ${2M}\choose{N_1+N_2}$ for $M, N_1, N_2 \in \mathbb{N},\,M\geq N_1,N_2$.
6650
Why $\sqrt{-1 \times -1} \neq \sqrt{-1}^2$?
104828
Show that $\cot \frac{\pi}{2m}\cot \frac{2\pi}{2m}\cot \frac{3\pi}{2m}...\cot \frac{(m-1)\pi}{2m}=1$