Read the two statements and choose the correct option.

I. If $\lvert \vec{a} \rvert = \lvert \vec{b} \rvert$, the projection of $\vec{a}$ on $\vec{b}$ equals the projection of $\vec{b}$ on $\vec{a}$.

II. If $\vec{a} \cdot \vec{b} < 0$, the angle between $\vec{a}$ and $\vec{b}$ is acute.

Explanation

1. 01

   I: the two projections are $\frac{\vec{a} \cdot \vec{b}}{\lvert \vec{b} \rvert}$ and $\frac{\vec{a} \cdot \vec{b}}{\lvert \vec{a} \rvert}$, equal when the magnitudes are equal. True.

2. 02

   II: $\vec{a} \cdot \vec{b} < 0$ means $\cos \theta < 0$, an obtuse angle. False.