When $- \pi \leq \theta \leq \pi$, $|1 - e^{i\theta}| \geq 2 |\theta|/\pi$
95266
Show $|t|\leq \pi \Rightarrow |e^{it}-1|\geq 2|t|/ \pi$
118687
Prove an inequality with a $\sin$ function: $\sin(x) > \frac2\pi x$ for $0<x<\frac\pi2$
25458
Prove inequalities $2\sqrt{n+1}-2 \leq 1 + 1/\sqrt{2} + 1/\sqrt{3} + .... + 1/\sqrt{n}\leq 2\sqrt{n}-1$
113411
If $E$ is generated by $E_1$ and $E_2$, then $[E:F]\leq [E_1:F][E_2:F]$?
118613
Proving an inequality: $|1-e^{i\theta}|\le|\theta|$
107601
Use of inequality $1 - \cos (x) \leq x^2 /2$
28822
$|x| - |y| \leq |x-y|?$
105622
How to show $ \sin x \geq \frac{2x}{\pi}, x \in [0, \frac{\pi}{2}]$?
4970
For $n \geq 2$, show that $n \nmid 2^{n}-1$
64096
Prove that $||z_1|-|z_2|| \leq |z_1-z_2|$.
133870
if $\alpha\leq\beta$ then there is $\gamma$ such as $\alpha+\gamma=\beta$
65562
Proving the inequality $\arctan\frac{\pi}{2}\ge1$
58969
A proof for the inequality $\sum_{i=0}^{t-2}{\frac{1}{t+3i}} \leq \frac{1}{2} $ for all $t \geq 2$
77576
Using the triangle inequalities to prove a bound in the complex plane
66707
How to prove this inequality? $ | z-1 | \le | | z | -1 | + | z| \cdot | \arg z | $
28125
Showing that $1 - \frac{x^2}2\leq\cos x$, $\forall x \in \mathbb{R}$
40837
Why $e^{i(π/3)} \ne -1$?