$\cos(2\pi t)=1$ for all real $t$?
131844
When does $(e^a)^b = e^{ab}$ hold?
66872
Exact values of $\cos(2\pi/7)$ and $\sin(2\pi/7)$
130058
Evaluate $\int_0^{\pi} e^{a\cos(t)}\cos(a\sin t)dt$
149801
prove that $TS = ST$
84730
use the fact that $\tan 2x=\sin2x \ /\cos2x$ to prove that $\tan 2x=2\tan x/(1-\tan^2x)$
52928
If $\mathrm{Tr}(A)=0$ then $T=R^{-1}AR$ has all entries on its main diagonal equal to $0$
96328
Proving $e^{i\pi} = -1$ without proving $e^{ix} = \cos x + i\sin x$
109853
Laplace transform of $\cos(at)$
30829
A question in Complex Analysis $\int_0^{2\pi}\log(1-2r\cos x +r^2)\,dx$
41191
How to prove this $\pi$ formula?
23901
Find every $z$s that fit $\cos(z) = -2$
109674
If $(I-T)^{-1}$ exists, can it always be written in a series representation?
125523
How to find $\int_{0}^{\pi/2} \log ({1+\cos x}) dx$ using real-variable methods?
11059
Verify the identity: $\tan^{-1} x +\tan^{-1} (1/x) = \pi /2$
143200
$f(r,\theta)=(r\cos\theta,r\sin\theta)$ Then
30002
Calculate the integral $\int_{0}^{2\pi}\frac{1}{a^{2}\cos^2t+b^{2}\sin^{2}t}dt$, by deformation theorem.
122169
Prove $\sin(\pi/2)=1$ using Taylor series