\[\begin{array}{l} {\text{Даны векторы }}\overrightarrow a = \left\{ {9;0;1} \right\}{\text{ и }}\overrightarrow b = \left\{ {8; - 3;4} \right\}.{\text{ Найти:}} \hfill \\ {\text{1) }}\overrightarrow a \cdot \left( {\overrightarrow b - \overrightarrow a } \right); \hfill \\ 2){\text{ }}\left| {\overrightarrow a } \right|; \hfill \\ 3){\text{ }}\cos \left( {\overrightarrow a ,\overrightarrow c } \right),{\text{ если }}\overrightarrow c = 2\overrightarrow a + \overrightarrow b ; \hfill \\ 4){\text{ }}\cos \beta {\text{ для }}\overrightarrow a ; \hfill \\ 5){\text{ }}\left| {\overrightarrow a + \overrightarrow b } \right|; \hfill \\ 6){\text{ п}}{{\text{р}}_{\overrightarrow b }}\overrightarrow a . \hfill \\ \end{array} \]