Question

Найдите сумму корней уравнения на промежутке [-п, 2п]​

Answer 1

$cos\left ( x+\frac{2\pi}{3} \right )+\sqrt{3}sinx=0\Leftrightarrow cosx\cdot cos\left (\frac{2\pi}{3}\right )-sinx\cdot sin\left ( \frac{2\pi}{3} \right )+\sqrt{3}sinx=0\Leftrightarrow \\\Leftrightarrow -\frac{1}{2}\cdot \left ( cosx+\sqrt{3}sinx \right )+\sqrt{3}sinx=0\Leftrightarrow -cosx-\sqrt{3}sinx+2\sqrt{3}sinx=0\Leftrightarrow \\\Leftrightarrow \sqrt{3}sinx-cosx=0\Leftrightarrow cos\left ( x+\frac{\pi}{3} \right )=0\Rightarrow x=\frac{\pi}{6}+\pi k,k\in \mathbb{Z}$

$-\frac{5\pi}{6}\in [-\pi;2\pi]\\\frac{\pi}{6}\in [-\pi;2\pi]\\\frac{7\pi}{6}\in [-\pi;2\pi]$