eInnerProduct

Example Find the angle between ${\bf A} = (1,1,2)$ and ${\bf B} = (-1,2,1)$ .

Example

$\displaystyle \cos{\theta} = \frac{a_{1}b_{1} + a_{2}b_{2} + a_{3}b_{3}}{\Vert(... ...Vert(b_{1},b_{2},b_{3})\Vert} = \frac{-1+2+2}{\sqrt{6}\sqrt{6}} = \frac{1}{2}.$

Note that $\theta$ must be in th interval $\displaystyle{[0, \frac{\pi}{2}]}$ . Thus, $\displaystyle{\theta = \frac{\pi}{3}}$ .