Trigonometric identity on $\cos \pi/7$
86454
How to prove $\cos\left(\pi\over7\right)-\cos\left({2\pi}\over7\right)+\cos\left({3\pi}\over7\right)=\cos\left({\pi}\over3 \right)$
12653
Prove $\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$
145559
Trigonometry problem on product of trig functions.
41191
How to prove this $\pi$ formula?
117200
Evaluation of $ \sum_{k=0}^n \cos k\theta $
149686
Combinatorics and trigonometry identity
123136
Proof of the identity: $c\sin \frac{A-B}{2} \equiv (a-b) \cos \frac{C}{2}$
104828
Show that $\cot \frac{\pi}{2m}\cot \frac{2\pi}{2m}\cot \frac{3\pi}{2m}...\cot \frac{(m-1)\pi}{2m}=1$
107067
Finding the argument of $z=1-\cos(2\theta)-i\sin(2\theta)$
76490
Proving that $\cos(\arcsin(x))=\sqrt{1-x^2}$
105238
Proving $\tan(\theta_1+\theta_2+\cdots+\theta_n)$ has the form $\frac{S_1-S_3+S_5+\cdots}{1-S_2+S_4+\cdots}$
104658
proving $\csc^2 \left( \frac{\pi}{7}\right)+\csc^2 \left( \frac{2\pi}{7}\right)+\csc^2 \left( \frac{4\pi}{7}\right)=8$
146047
Proving that $\cos(2\pi/n)$ is algebraic
11059
Verify the identity: $\tan^{-1} x +\tan^{-1} (1/x) = \pi /2$
52413
Show that $\tan{(\pi/7)} \tan{(2\pi/7)}\tan{(3\pi/7)}=\sqrt{7}$
69478
Deducing a $\cos (kx)$ summation from the $e^{ikx}$ summation
122169
Prove $\sin(\pi/2)=1$ using Taylor series