4

2

0

-2

$\frac{3}{2}$

$\cos ^2 \frac{\alpha}{2}+\cos ^2 \frac{\beta}{2}+\cos ^2 \frac{\gamma}{2}$

$3 \sin (\alpha+\beta+\gamma)$

$\cos (\alpha+\beta)+\cos (\beta+\gamma)+\cos (\gamma+\alpha)$

$4 \operatorname{cis} \frac{2 \pi}{5}$

$4 \operatorname{cis} \frac{3 \pi}{5}$

$4 \operatorname{cis} \frac{4 \pi}{5}$

$4 \operatorname{cis} \frac{6 \pi}{5}$

$\pm(1+2 i)$

$\pm(3+i)$

$\pm(1+7 i)$

$\pm(7-i)$