Question
If $\cos \alpha$, $\cos \beta$, and $\cos \gamma$ are the direction cosines of a vector $\vec{a}$, then $\cos^2 \alpha + \cos^2 \beta + \cos^2 \gamma$ is equal to
If $\cos \alpha$, $\cos \beta$, and $\cos \gamma$ are the direction cosines of a vector $\vec{a}$, then $\cos^2 \alpha + \cos^2 \beta + \cos^2 \gamma$ is equal to