Existence of formulae for sines/cosines of products of angles in terms of sines/cosines of original angles?
105774
How is $ \cos (\alpha / \beta) $ expressed in terms of $\cos \alpha $ and $ \cos \beta $?
9479
$\sum \cos$ when angles are in arithmetic progression
72157
Elementary proof of tangent half angle formula
77435
Analytic solution for angle of minimum deviation?
58958
How to understand dot product is the angle's cosine?
84420
When is $\sin(x) = \cos(x)$?
94283
Different ways finding the derivative of $\sin$ and $\cos$.
147886
Proof of the angle sum identity for $\sin$
61343
Prove that if $\alpha, \beta, \gamma$ are angles in triangle, then $(tan(\frac{\alpha}{2}))^2+(tan(\frac{\beta}{2}))^2+(tan(\frac{\gamma}{2}))^2\geq1$
100777
Finding the derivatives of sin(x) and cos(x)
111199
Does there exist a formula for product of the primitive $ n $th roots of unity.
51979
Is there a geometrical method to prove $x<\frac{\sin x +\tan x}{2}$?
135543
Proof of Angles going beyond 90 degrees in Trigonometry
31575
Solving trigonometric equations of the form $a\sin x + b\cos x = c$
30480
Continued product in $\sin$ series
156890
If $f$ and $g$ satisfy the sine/cosine addition formulae, then what is $g'(0)$?
75570
Easy way of memorizing values of sine, cosine, and tangent