$\arctan (x) + \arctan(1/x) = \frac{\pi}{2}$
11059
Verify the identity: $\tan^{-1} x +\tan^{-1} (1/x) = \pi /2$
131310
Evaluating $\dfrac{1}{\sin(2x)} + \dfrac{1}{\sin(4x)} + \dfrac{1}{\sin(8x)} + \dfrac{1}{\sin(16x)}$
34905
Proving that $\int_0^1 \frac{\arctan x}{x}\ln\left(\frac{1+x^2}{(1-x)^2}\right)dx=\frac{\pi^3}{16}$
120953
Show that, $2\arctan\left(\frac{1}{3}\right)+2\arcsin\left(\frac{1}{5\sqrt2}\right)-\arctan\left(\frac{1}{7}\right)=\frac{\pi}{4}$
17769
Show that $\frac{\sin x}{\cos 3x}+\frac{\sin 3x}{\cos 9x}+\frac{\sin 9x}{\cos 27x} = \frac{1}{2}\left(\tan 27x-\tan x\right)$
60288
Why is $\arctan(x)=x-x^3/3+x^5/5-x^7/7+\dots$?
151462
Find $\int \limits_0^1 \int \limits_x^1 \arctan \bigg(\frac yx \bigg) \, \, \, dx \, \, dy$
155539
Evaluating the limit $\lim_{x \to 0+}\left(\frac{1}{x}-\frac{1}{\arctan(x)}\right)$
33791
Is it generally true that $\arcsin \theta + \arccos \theta = \frac{\pi}{2}$?
51979
Is there a geometrical method to prove $x<\frac{\sin x +\tan x}{2}$?
25032
How to calculate $\theta = \arcsin\left(\frac{1}{2}\right)$ with given four function calculator?
102932
Integral $\int_0^\infty \frac{\arctan(x) dx}{x(1+x^2)}$?
115128
How do I show this $\cos^2(\arctan(x))=\frac{1}{1+x^2}$
25065
What is $\arctan(x) + \arctan(y)$
95403
Evaluating $\int \frac{\sec^2 x}{(\sec x + \tan x )^{{9}/{2}}}\,\mathrm dx$
113781
How can I calculate $\lim_{x\to 0} \frac{\arctan(x)-\arcsin(x)}{x^3}$ without L'Hôpital?
119815
Why is $\tan((1/2)\pi)$ undefined?