How can I graphically show cos(A+B) = cosA cosB + sinA sinB?
34049
How can I understand and prove the "sum and difference formulas" in trigonometry?
37108
Solve $\cos(z)=\frac 34+\frac i4$
145559
Trigonometry problem on product of trig functions.
98043
How to visualize Reverse Triangle Inequality $||\mathbf{a}| − |\mathbf{b}|| ≤ |\mathbf{a} − \mathbf{b}|$?
121263
Using $\sin()$ or $\cos()$ for computing SHM?
16866
How to Prove $a^3 \cos (B-C) + b^3 \cos (C-A)+ c^3 \cos (A-B)=3abc$?
81102
Cosine of the sum of two solutions of trigonometric equation $a\cos \theta + b\sin \theta = c$
40556
Why is $\sin(\alpha+\beta)=\sin\alpha\cos\beta+\sin\beta\cos\alpha$
17188
Simplify $\cos(n \pi)$ and $\sin(n \pi)$ when n is an integer
29370
Trig integral $\int ( \cos{x} + \sin{x}\cos{x}) \, dx $
108245
Solving the complex equation $\sin(z) = \cos(z)$
93212
Express $\sqrt{3}\sin\theta - \cos\theta$ as: $a\cos (\theta + \alpha) $
27628
Solving $a \sin\theta + b \cos\theta = c$
24656
Proving that $\frac{\csc\theta}{\cot\theta}-\frac{\cot\theta}{\csc\theta}=\tan\theta\sin\theta$
56059
If $\frac{\sin^4 x}{a}+\frac{\cos^4 x}{b}=\frac{1}{a+b}$, then show that $\frac{\sin^6 x}{a^2}+\frac{\cos^6 x}{b^2}=\frac{1}{(a+b)^2}$
123133
If, in a triangle, $\cos(A) + \cos(B) + 2\cos(C) = 2$ prove that the sides of the triangle are in AP
17769
Show that $\frac{\sin x}{\cos 3x}+\frac{\sin 3x}{\cos 9x}+\frac{\sin 9x}{\cos 27x} = \frac{1}{2}\left(\tan 27x-\tan x\right)$