If are three mutually perpendicular vectors of equal magnitude, prove that is equally inclined with…

If $\vec{a}, \vec{b}, \vec{c}$ are three mutually perpendicular vectors of equal magnitude, prove that $(\vec{a} + \vec{b} + \vec{c})$ is equally inclined with vectors $\vec{a}, \vec{b}$ and $\vec{c}$.