Question

Cos x+ 2cosx + Sinx=0 solve the equation for the interval [0,2pi]

Answer 1

cos²(x) + 2cos(x) + sin²(x) = 0
 Note: cos²(x) + sin²(x) = 1
2cos(x) + 1 = 0
2cos(x) = -1
cos(x) = $- \frac{1}{2}$
120 degrees and 240 degrees → $\frac{2}{3} \pi$ and $\frac{4}{3} \pi$