Is $\tan(\alpha/2)=(1-\cos\alpha)/\sin \alpha, \,?$
72157
Elementary proof of tangent half angle formula
113080
Prove $\tan\big(\frac{\pi}{2} -\theta \big) = \cot \theta$
45227
If $\sin \theta+\cos\theta+\tan\theta+\cot\theta+\sec\theta+\csc\theta=7$, then $\sin 2\theta$ is a root of $x^2 -44x +36=0$ My own bonafide attempt.
65239
Find $\lim_{x \to 0} \frac{x - \tan(x)}{x - \sin(x)}$
107067
Finding the argument of $z=1-\cos(2\theta)-i\sin(2\theta)$
145632
Proving $\frac{1}{\cos^2\alpha}<\frac{\tan\beta-\tan\alpha}{\beta-\alpha}<\frac{1}{\cos^2\beta}$
39266
Show that $\tan {\pi \over 8} = \sqrt 2 - 1$
33791
Is it generally true that $\arcsin \theta + \arccos \theta = \frac{\pi}{2}$?
123997
Finding an expression for $\tan (a+ b + y)$ which involves only $\tan a, \tan b,$ and $\tan y$.
617
Find θ: $β=\arctan\frac{(R+r)·\sin(θ)-r·\sin(θ(1+\frac{R}{r}))}{(R+r)·\cos(θ)-r·\cos(θ(1+\frac{R}{r}))}$
101448
Is $\sin^2(z) + \cos^2(z)=1$ still true for $z \in \Bbb{C}$?
45092
Integrating a function of tan inverse
51979
Is there a geometrical method to prove $x<\frac{\sin x +\tan x}{2}$?
30600
Why does $\tan^{-1}(1)+\tan^{-1}(2)+\tan^{-1}(3)=\pi$?
154219
Help with integral $\int\frac{1}{\sqrt{\tan x}}dx$
33905
Prove the following trigonometric identity: $\frac{\tan A+\sec A-1}{\tan A-\sec A+1}=\frac{1+\sin A}{\cos A}$
142673
Evaluate $\tan^{2}(20^{\circ}) + \tan^{2}(40^{\circ}) + \tan^{2}(80^{\circ})$