Prove that the function $x\mapsto\sin(x^{2})$ is not periodic
35754
Is $f(x)=\sin(x^2)$ periodic?
35953
Prove that a function is not injective
68171
Non-trigonometric Continuous Periodic Functions
49385
Proving $\forall x (A\to B) \to(A \to \forall x B):x\notin \mbox{free}(A)$ in a Hilbert system where it is not an axiom
72044
prove $x \mapsto x^2$ is continuous
23288
Prove that $x^2<\sin x \tan x$ as $x \to 0$
134575
Show that the mapping $f → f~'$ from $C^1([0 , 1])$ to $C([0 , 1])$ is not continuous.
121979
Pointwise convergence of sine series of $x^{-2}$
97391
Prove that $(C^1[0,1], \|\cdot\|)$ is not a Banach space
103285
Limit of a periodic function
144331
Periodic function implies periodic primitive?
26749
$\mathbb{Z}[X]/(X^2-1)$ is not isomorphic with $\mathbb{Z}\times \mathbb{Z}$
64130
Prove that $\mathbb{Q}^{\times}$ not isomorphic to $\mathbb{Z}^{n}$
6186
An Integrable function which is not essentially bounded on any subinterval of $[0,1]$
40041
Proof of Non-Ordering of Complex Field
99726
Proving that a function is not a contraction
86860
Continuity of differentiable function $x^2\sin(1/x)$