Trigonometric Expression for $1 + \cos \alpha + \cos 2\alpha + \cdots + \cos n \alpha$ using complex numbers
9479
$\sum \cos$ when angles are in arithmetic progression
31575
Solving trigonometric equations of the form $a\sin x + b\cos x = c$
100907
$\sin\alpha + \sin\beta + \sin\gamma = 4\cos{\frac{\alpha}{2}}\cos{\frac{\beta}{2}}\cos{\frac{\gamma}{2}}$ when $\alpha + \beta + \gamma = \pi$
46394
If $\frac{\cos \alpha}{\cos \beta}+\frac{\sin \alpha}{\sin \beta}=-1$, find $\frac{\cos^3\beta}{\cos \alpha}+\frac{\sin^3\beta}{\sin \alpha}$.
35244
Prove $\sin^2\theta + \cos^2\theta = 1$
122181
Application of Complex Numbers
105238
Proving $\tan(\theta_1+\theta_2+\cdots+\theta_n)$ has the form $\frac{S_1-S_3+S_5+\cdots}{1-S_2+S_4+\cdots}$
37108
Solve $\cos(z)=\frac 34+\frac i4$
101448
Is $\sin^2(z) + \cos^2(z)=1$ still true for $z \in \Bbb{C}$?
120092
Express the complex numbers given in Problem in the form $a+ib$
40869
Solving Trigonometric Limits
83359
Complex number identity by trigonometry
100320
Prove that $\cos\frac {2\pi}{7}+ \cos\frac {4\pi}{7}+ \cos\frac {8\pi}{7}=-\frac{1}{2}$
154216
Solve $\sin(z) = z$ in complex numbers
62109
$\int_{-\infty}^{\infty} \frac{\cos(αx)}{(x^2+1)(x^2+4)} \mathrm dx$ using Complex methods
104321
Prove that $1 + \cos\alpha + \cos\beta + \cos\gamma = 0$
26501
Proof using complex numbers