Mathematics

Problem

Let

\vec{a} = 2\hat{i} + \hat{j} - \hat{k}

\vec{b} = ((\vec{a} \times (\hat{i} + \hat{j})) \times \hat{i}) \times \hat{i}

. Then the square of the projection of

\vec{a}

\vec{b}

is:

\frac{1}{3}

\frac{2}{3}

\frac{1}{5}