Proving periodicity of sine and cosine
6465
How to prove periodicity of $\sin(x)$ or $\cos(x)$ starting from the Taylor series expansion?
5459
Convergent subsequence for sin(n)
99782
$a_{n+1}=|a_n|-a_{n-1} \implies a_n \; \text{is periodic}$
129890
Proving inequality $|\sin(n\theta) |\le n\sin\theta$
141137
Can we use sine and cosine graphs for varying temperatures?
33489
|f| is periodic implies f is periodic
13566
Is it possible to detect periodicity of an analytic function from its Taylor series coefficients at a point?
7878
Proving that a doubly-periodic entire function $f$ is constant.
112517
Proving bounds of a harmonic series
146047
Proving that $\cos(2\pi/n)$ is algebraic
35754
Is $f(x)=\sin(x^2)$ periodic?
114411
Simple Proof of the Euler Identity $\exp{i\theta}=\cos{\theta}+i\sin{\theta}$
70301
$\sin(n)$ subsequence limits set
48586
Prove: $\cot x=\sin x\,\sin\left(\frac{\pi}{2}-x\right)+\cos^2x\,\cot x$
17188
Simplify $\cos(n \pi)$ and $\sin(n \pi)$ when n is an integer
152701
A question on periodicity of complex functions
158230
prove that a non constant periodic, continuous function has a "smallest period"