Help with trigonometry identity derivation
104658
proving $\csc^2 \left( \frac{\pi}{7}\right)+\csc^2 \left( \frac{2\pi}{7}\right)+\csc^2 \left( \frac{4\pi}{7}\right)=8$
87934
Deducing $\sin x + \cos x \ge 1$ from $(\sin x + \cos x)^2 = 1 + 2 \sin x \cos x$
147886
Proof of the angle sum identity for $\sin$
27132
Can't figure out how $\sin\left(\tan^{-1}(x)\right)=\frac{x}{\sqrt {x^2+1}}$
24656
Proving that $\frac{\csc\theta}{\cot\theta}-\frac{\cot\theta}{\csc\theta}=\tan\theta\sin\theta$
89003
Finding a trigonometric polynomial
149686
Combinatorics and trigonometry identity
40556
Why is $\sin(\alpha+\beta)=\sin\alpha\cos\beta+\sin\beta\cos\alpha$
86454
How to prove $\cos\left(\pi\over7\right)-\cos\left({2\pi}\over7\right)+\cos\left({3\pi}\over7\right)=\cos\left({\pi}\over3 \right)$
13297
Prove the following trigonometric identity without a calculator involved
44119
Prove that $\cos (A + B)\cos (A - B) = {\cos ^2}A - {\sin ^2}B$
86894
Finding solution of a Trigonometric equation
84420
When is $\sin(x) = \cos(x)$?
1210
Write an expression for $(\cos θ + i\sin θ)^4$ using De Moivre’s Theorem.
116270
Functional equations leading to sine and cosine
94283
Different ways finding the derivative of $\sin$ and $\cos$.
149447
Proving $\sin (x)=\cos (90^\circ-x)$