TeX Quellcode:
\varphi = \arccos \left( \dfrac{ a_1 b_1 + a_2 b_2 + a_3 b_3}{\sqrt{{a_1}^2+{a_2}^2+{a_3}^2} \cdot \sqrt{{b_1}^2+{b_2}^2+{b_3}^2}} \right) = \arccos \left( \dfrac {\vec{a}^{\,T} \cdot \vec{b}}{\left|\vec{a}\right| \cdot \left|\vec{b}\right|} \right)