318. Find the angles formed by the vector $\bar{a}\{-2 ; 2 ; 1\}$ with the coordinate axes.
Solution. Using formulas (17), we get: $\cos \alpha=\frac{-2}{\sqrt{(-2)^{2}+2^{2}+1^{2}}}=-\frac{2}{3}, \cos \beta=\frac{2}{3}, \quad \cos \gamma=\frac{1}{3}$, hence $\alpha \approx 131^{\circ} 49^{\prime}, \beta \approx 48^{\circ} 11^{\prime}, \gamma \approx 70^{\circ} 32^{\prime}$.