Mathematics

Problem

\vec{a}, \vec{b}

and

\vec{c}

are non-coplanar unit vectors such that

\vec{a} \times (\vec{b} \times \vec{c}) = \frac{1}{\sqrt{2}}(\vec{b} + \vec{c})

, then the angle between

\vec{a}

and

\vec{b}

is a.

\frac{3\pi}{4}

\frac{\pi}{4}

\frac{\pi}{2}

\pi