Trigonometric ratios proof problems
14410
If $(1+ \cos A) (1+ \cos B) (1+\cos C)= y = (1- \cos A) (1-\cos B) (1-\cos C)$ then $y = \pm \sin A \sin B \sin C$
46353
Proof that $\cos(\pi/3)=1/2$
64255
Trigonometry problem
126574
Proving $\prod_k \sin \pi k / n = n / 2^{n-1}$
40596
Proving a relation between inradius ,circumradius and exradii in a triangle
44119
Prove that $\cos (A + B)\cos (A - B) = {\cos ^2}A - {\sin ^2}B$
7296
Prove $(1-\cos x)/\sin x = \tan x/2$
77810
Solving Trigonometric Derivatives
13297
Prove the following trigonometric identity without a calculator involved
143050
If $\tan(\frac{\pi}{4}+\frac{y}{2})=\tan^3(\frac{\pi}{4}+\frac{x}{2})$,then prove that $\sin y=\frac{\sin x(3+\sin^2 x)}{(1+3\sin^2 x)}$
73512
Trigonometry Olympiad Question
88432
A problem on range of a trigonometric function: what is the range of $\frac{\sqrt{3}\sin x}{2+\cos x}$?
138847
Tricky trigonometric sum evaluation
106355
How to prove Lagrange trigonometric identity
90226
Proving trigonometric equation $\cos(36^\circ) - \cos(72^\circ) = 1/2$
32792
Proving: $\cos A \cdot \cos 2A \cdot \cos 2^{2}A \cdot \cos 2^{3}A ... \cos 2^{n-1}A = \frac { \sin 2^n A}{ 2^n \sin A } $
54512
How do I prove: $\cos (\theta + 90^\circ) \equiv - \sin \theta $