This equation computes the Vector Norm, the positive length, of a vector from the Euclidean three space x,y,z components of the vector.
There all kinds of vectors applied in physics for forces, positions, velocities, acceleration, etc. The position vector, often represented by `rvec` can be decomposed into its components parallel to the Euclidean three-space axes: `vecr = r_xrhati + r_yhatj + r_zhatk`
Similarly, a velocity vector could be decomposed into its Euclidean components as: `vecv = v_xrhati + v_yhatj + v_zhatk`