Prove the following trigonometric identity without a calculator involved
9479
$\sum \cos$ when angles are in arithmetic progression
10289
Need help in proving that $\frac{\sin\theta - \cos\theta + 1}{\sin\theta + \cos\theta - 1} = \frac 1{\sec\theta - \tan\theta}$
127380
Use vectors to prove $\cos(\beta - \alpha) = \cos \alpha \cos\beta + \sin\alpha \sin\beta$
1859
Proving $\arctan(\sqrt{x^2+1}-x)=\frac{\pi}{4}-\frac{1}{2}\arctan(x)$
55869
Use the Maclaurin series to prove that $e^{i\theta} = cos(\theta) + isin(\theta)$
95633
Help with this trigonometry problem
11059
Verify the identity: $\tan^{-1} x +\tan^{-1} (1/x) = \pi /2$
33905
Prove the following trigonometric identity: $\frac{\tan A+\sec A-1}{\tan A-\sec A+1}=\frac{1+\sin A}{\cos A}$
31575
Solving trigonometric equations of the form $a\sin x + b\cos x = c$
48824
Prove: $ \frac{1}{\sin 2x} + \frac{1}{\sin 4x } + \cdots + \frac{1 }{\sin 2^n x} = \cot x - \cot 2^n x $
12741
How to prove that: $\tan(3\pi/11) + 4\sin(2\pi/11) = \sqrt{11}$
50509
Prove that $\int_0^4 \frac{\ln x}{\sqrt{4x-x^2}}~dx=0$ (without trigonometric substitution)
33100
Trigonomnetric equality involving tg
87934
Deducing $\sin x + \cos x \ge 1$ from $(\sin x + \cos x)^2 = 1 + 2 \sin x \cos x$
51979
Is there a geometrical method to prove $x<\frac{\sin x +\tan x}{2}$?
85872
Prove $1 + \tan^2\theta = \sec^2\theta$
53307
how to strictly prove $\sin x<x$ for $0<x<\frac{\pi}{2}$