Prove that $\cos^2\theta+\sin^2\theta=1$
35244
Prove $\sin^2\theta + \cos^2\theta = 1$
44391
How can I prove $n - 2\sqrt{n} = \Theta(n)$
46353
Proof that $\cos(\pi/3)=1/2$
147684
Prove that $\sin \theta=\frac{3 \sin \alpha+\sin^3 \alpha}{1+3\sin^2 \alpha}$ using given condition
117680
Prove that $|e^{i\theta_1}-e^{i\theta_2}| \leq |\theta_1 - \theta_2|$
114414
Sum of $\sum_{k=1}^n\sin{k\theta}$
123136
Proof of the identity: $c\sin \frac{A-B}{2} \equiv (a-b) \cos \frac{C}{2}$
113080
Prove $\tan\big(\frac{\pi}{2} -\theta \big) = \cot \theta$
40556
Why is $\sin(\alpha+\beta)=\sin\alpha\cos\beta+\sin\beta\cos\alpha$
73538
solving $\cos z + \sin z = i$
23288
Prove that $x^2<\sin x \tan x$ as $x \to 0$
7296
Prove $(1-\cos x)/\sin x = \tan x/2$
52311
Prove that $0 \le \frac{1+\cos\theta}{2+\sin\theta} \le \frac{4}{3}$ for all real $\theta$.
71413
Proving complex series $1 + \cos\theta + \cos2\theta +... + \cos n\theta $
120148
prove this properties of triangles trigonometric question
63679
Picture/intuitive proof of $\cos(3 \theta) = 4 \cos^3(\theta)-3\cos(\theta)$?
29604
How to solve $\sin x +\cos x = 1$?