Why is $\cos(\cos(\cos(0))) = 0.739$ (with infinite $\cos()$)?
121319
Why do I get a converging result when pressing cosine multiple times on a calculator?
84420
When is $\sin(x) = \cos(x)$?
25569
Intuitive understanding of the derivatives of $\sin x$ and $\cos x$
2167
Find the limit $\lim\limits_{x\to \infty}(e^{-x}+2\cos3x)$, or show that it does not exist.
23727
How can I deduce $\cos\pi z=\prod_{n=0}^{\infty}(1-4z^2/(2n+1)^2)$?
9343
Why does $\frac{1 }{ 99989999}$ generate the Fibonacci sequence?
129319
Weird "hidden answer" in $2\tan(2x)=3\text{cot}(x)$
117583
Why does $\sum_{n=0}^\infty (\sin{\frac{1}{n}})(\sinh{\frac{1}{n}})(\cos n)$ converge
141787
Anybody know a proof of $\prod_{n=1}^\infty\cos(x/2^n)=\sin x/x$.
126701
How to prove that $d \sin(x)/dx = \cos(x)$ without circular logic such as L'Hôpital's rule?
68968
Math.cos inaccurancy
111705
Why does $\frac{1+t}{(1-t)^3}=\sum_{n=0}^{\infty}(1+n)^2t^n$
126264
Does the series $\sum \limits _{n=0}^{\infty} \cos(n\pi)$ converge or diverge?
106803
How to see $\cos x \leq \exp(-x^2/2)$ on $x \in [0,\pi/2]$?
286
Is it true that $0.999999999\ldots=1$?
118586
Confused About Trigonometric Substitution
40556
Why is $\sin(\alpha+\beta)=\sin\alpha\cos\beta+\sin\beta\cos\alpha$