$$\color{rgb(127,0,0)}-\frac{\pi}{3}$$

$$\color{rgb(0,127,127)}\frac{\pi}{2}$$

$$\color{rgb(0,0,255)}\frac{5\pi}{6}$$

$$\color{rgb(0,0,0)}\text{Hypoth}\grave{e} \text{ses : }\left\{ \begin{array}{l} {\left( \overrightarrow {CB};\overrightarrow {CA} \right)=-\frac{\pi}{3} } \\ {\left( \overrightarrow {BC};\overrightarrow {BA} \right)=\frac{\pi}{2}} \\ {\left( \overrightarrow {AD};\overrightarrow {AB} \right)=\frac{5\pi}{6}} \end{array} \right.$$