$i = i \implies -1 = 1$?
3712
Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$?
146795
Proof If $AB-I$ Invertible then $BA-I$ invertible.
95057
Possible fake proof of $1= -1$
30860
Prove that $f(x)=0$ in $[-1,1]$.
41779
Is $x/x$ equal to $1$
146339
Proof of -(-v)=v in a vector space
155285
difficulty of accepting $i^2 = -1$ for first timers
96328
Proving $e^{i\pi} = -1$ without proving $e^{ix} = \cos x + i\sin x$
3301
If $AB = I$ then $BA = I$
111024
Does $gHg^{-1}\subseteq H$ imply $gHg^{-1}= H$?
156235
Are $x \cdot 0 = 0$, $x \cdot 1 = x$, and $-(-x) = x$ axioms?
6539
Prove $\sum_{i=1}^n i! \cdot i = (n+1)! - 1$?
80004
Why is $1/i$ equal to $-i$?
109674
If $(I-T)^{-1}$ exists, can it always be written in a series representation?
101320
How to tell $i$ from $-i$?
124209
How is $\ln(-1) = i\pi$?
33542
When is $A- B = B- A$?