If $\sin\theta+\cos\theta=1$ prove that $\cos\theta-\sin\theta=\pm1$
53135
Find $4\cos\theta-3\sin\theta$, given that $4\sin \theta +3\cos \theta = 5$
63679
Picture/intuitive proof of $\cos(3 \theta) = 4 \cos^3(\theta)-3\cos(\theta)$?
45619
Prove: $|a\sin x+b \cos x|\leq \sqrt{a^2+b^2}$
60709
How do I get $\cos{\theta} \lt \frac{\sin{\theta}}{\theta} \lt 1$?
127380
Use vectors to prove $\cos(\beta - \alpha) = \cos \alpha \cos\beta + \sin\alpha \sin\beta$
44438
Prove : $\frac{\cos(x_1) +\cos(x_2) +\cdots+\cos(x_{10})}{\sin(x_1) +\sin(x_2) +\cdots+\sin(x_{10})} \ge 3$
87934
Deducing $\sin x + \cos x \ge 1$ from $(\sin x + \cos x)^2 = 1 + 2 \sin x \cos x$
29604
How to solve $\sin x +\cos x = 1$?
52311
Prove that $0 \le \frac{1+\cos\theta}{2+\sin\theta} \le \frac{4}{3}$ for all real $\theta$.
10289
Need help in proving that $\frac{\sin\theta - \cos\theta + 1}{\sin\theta + \cos\theta - 1} = \frac 1{\sec\theta - \tan\theta}$
81102
Cosine of the sum of two solutions of trigonometric equation $a\cos \theta + b\sin \theta = c$
142835
Proving :$\arctan(1)+\arctan(2)+ \arctan(3)=\pi$
148207
Express $\cos 6\theta $ in terms of $\cos \theta$
104321
Prove that $1 + \cos\alpha + \cos\beta + \cos\gamma = 0$
13297
Prove the following trigonometric identity without a calculator involved
100895
Prove $1 + \cos 2C - \cos 2A - \cos 2B = 4\sin A\sin B\cos C$ for $A$, $B$, $C$ the angles of a triangle
143200
$f(r,\theta)=(r\cos\theta,r\sin\theta)$ Then