What trigonometric identity was used?
9479
$\sum \cos$ when angles are in arithmetic progression
135543
Proof of Angles going beyond 90 degrees in Trigonometry
24656
Proving that $\frac{\csc\theta}{\cot\theta}-\frac{\cot\theta}{\csc\theta}=\tan\theta\sin\theta$
33905
Prove the following trigonometric identity: $\frac{\tan A+\sec A-1}{\tan A-\sec A+1}=\frac{1+\sin A}{\cos A}$
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.
120569
Trigonometric Functions And Identities Question .
33396
Generalizing a Trig Identity
124897
How many ways are there to define sine and cosine?
94283
Different ways finding the derivative of $\sin$ and $\cos$.
45725
Derivation of an identity with beta function.
86894
Finding solution of a Trigonometric equation
48881
Verification the integral identity $\int_0^\pi \ln(1+\alpha\cos(x))dx=\pi\ln\left(\frac{1+\sqrt{1-\alpha^2}}{2}\right)$.
11711
Prove trigonometry identity for $\cos A+\cos B+\cos C$
69077
When the trig functions moved from the right triangle to the unit circle?
10289
Need help in proving that $\frac{\sin\theta - \cos\theta + 1}{\sin\theta + \cos\theta - 1} = \frac 1{\sec\theta - \tan\theta}$
64268
How does a calculator calculate the sine, cosine, tangent using just a number?
67172
What's the intuition behind the identities $\cos(z)= \cosh(iz)$ and $\sin(z)=-i\sinh(iz)$?