How is $\cos (\pi/2+h)$ equal to $-\sin(h)$?
54512
How do I prove: $\cos (\theta + 90^\circ) \equiv - \sin \theta $
30429
How to prove $\cos \frac{2\pi }{5}=\frac{-1+\sqrt{5}}{4}$?
31922
Integral of $\sin x \cos x$ using two methods differs by a constant?
20016
How to integrate $\int_0^{\pi/2}\frac{\sin^nx}{\sin^nx+\cos^nx}dx$?
83290
How is the value of $\pi$ ( Pi ) actually calculated?
118586
Confused About Trigonometric Substitution
118701
Evaluate $\int_{0}^{\frac{\pi }{2}}\frac{x dx}{\sin x +\cos x}$
10289
Need help in proving that $\frac{\sin\theta - \cos\theta + 1}{\sin\theta + \cos\theta - 1} = \frac 1{\sec\theta - \tan\theta}$
123892
What is $\int_{-\pi}^\pi \cos(nx)\cos(mx)\,dx$?
90226
Proving trigonometric equation $\cos(36^\circ) - \cos(72^\circ) = 1/2$
122169
Prove $\sin(\pi/2)=1$ using Taylor series
55179
How to find the exact value of $ \cos(36^\circ) $?
48586
Prove: $\cot x=\sin x\,\sin\left(\frac{\pi}{2}-x\right)+\cos^2x\,\cot x$
126701
How to prove that $d \sin(x)/dx = \cos(x)$ without circular logic such as L'Hôpital's rule?
118330
How do we know what the integral of $\sin (x)$ is?
48086
Why is this series of square root of twos equal $\pi$?
105774
How is $ \cos (\alpha / \beta) $ expressed in terms of $\cos \alpha $ and $ \cos \beta $?