Show that $a \cos \theta + b \sin \theta = \sqrt{a^2+b^2} \cos (\theta - \varphi)$
55436
Why does $A\sin{k(x+c)}=a\sin{kx}+b\cos{kx}$ imply that $A=\sqrt{a^2+b^2}$ and $\tan{c}=-b/a$?
77002
$\int_{0}^{\frac{\pi}{2}}\frac{d\theta}{a + \sin^2(\theta)} = \frac{\pi}{2\sqrt{a(a+1)}}$, for $a > 0$
45227
If $\sin \theta+\cos\theta+\tan\theta+\cot\theta+\sec\theta+\csc\theta=7$, then $\sin 2\theta$ is a root of $x^2 -44x +36=0$ My own bonafide attempt.
77212
Show that for any real constants a and b, where b > 0, (n + a) b = Θ(n b ).
156162
Are $\cos^2 \theta$ and $\cos \theta^2$ the same?
81102
Cosine of the sum of two solutions of trigonometric equation $a\cos \theta + b\sin \theta = c$
33791
Is it generally true that $\arcsin \theta + \arccos \theta = \frac{\pi}{2}$?
55869
Use the Maclaurin series to prove that $e^{i\theta} = cos(\theta) + isin(\theta)$
147886
Proof of the angle sum identity for $\sin$
11711
Prove trigonometry identity for $\cos A+\cos B+\cos C$
16270
Trigonometry question: $\sin^2(A) + \sin^2(B) - \sin^2(C) = 2\sin(A)\sin(B)\cos(C).$
90226
Proving trigonometric equation $\cos(36^\circ) - \cos(72^\circ) = 1/2$
617
Find θ: $β=\arctan\frac{(R+r)·\sin(θ)-r·\sin(θ(1+\frac{R}{r}))}{(R+r)·\cos(θ)-r·\cos(θ(1+\frac{R}{r}))}$
75679
How to prove that $2 \arctan\sqrt{x} = \arcsin \frac{x-1}{x+1} + \frac{\pi}{2}$
138575
Proof that $\cos^2(x)\cosh^2(y) + \sin^2(x)\sinh^2(y) = -1 + \sin^2(x) - \sinh^2(y)$
143200
$f(r,\theta)=(r\cos\theta,r\sin\theta)$ Then
53135
Find $4\cos\theta-3\sin\theta$, given that $4\sin \theta +3\cos \theta = 5$