prove trigonometry identity for $\sin\alpha+\sin2\alpha+\sin3\alpha+...+\sin N\alpha$, whithout using induction
5080
How can we sum up $\sin$ and $\cos$ series when the angles are in arithmetic progression?
128309
Use Mathematical Induction to prove that $\frac{1}{1 \cdot 2} + \frac{1}{2 \cdot 3} +...+\frac{1}{n(n+1)}=1-\frac{1}{n+1}$
143050
If $\tan(\frac{\pi}{4}+\frac{y}{2})=\tan^3(\frac{\pi}{4}+\frac{x}{2})$,then prove that $\sin y=\frac{\sin x(3+\sin^2 x)}{(1+3\sin^2 x)}$
13297
Prove the following trigonometric identity without a calculator involved
57750
Solve identity: $\frac {\sin x}{1-\cos x} = \frac {1+\cos x}{\sin x}$
104384
Trigonometric identity: $\frac {\tan\theta}{1-\cot\theta}+\frac {\cot\theta}{1-\tan\theta} =1+\sec\theta\cdot\csc\theta$
33905
Prove the following trigonometric identity: $\frac{\tan A+\sec A-1}{\tan A-\sec A+1}=\frac{1+\sin A}{\cos A}$
83359
Complex number identity by trigonometry
120569
Trigonometric Functions And Identities Question .
11059
Verify the identity: $\tan^{-1} x +\tan^{-1} (1/x) = \pi /2$
33396
Generalizing a Trig Identity
7296
Prove $(1-\cos x)/\sin x = \tan x/2$
14386
Proof of an equality involving cosine $\sqrt{2 + \sqrt{2 + \cdots + \sqrt{2 + \sqrt{2}}}}\ =\ 2\cos (\pi/2^{n+1})$
139065
Proving $\csc\frac\alpha2+\csc\frac\beta2+\csc\frac\gamma2 \ge 6$, where $\alpha$, $\beta$, $\gamma$ are the angles of a triangle
17769
Show that $\frac{\sin x}{\cos 3x}+\frac{\sin 3x}{\cos 9x}+\frac{\sin 9x}{\cos 27x} = \frac{1}{2}\left(\tan 27x-\tan x\right)$
37040
Prove reduction formula for $\int \cos^n (x)\sin^m (x) \, dx$
31575
Solving trigonometric equations of the form $a\sin x + b\cos x = c$