Compare and contrast apparent magnitude and luminosity

i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.