# Spherical Harmonics expansion

## Main Question or Discussion Point

Hi,
I need expand a spherical function(real function not a complex function) in terms of spherical harmonics. Expansion coefficients are complex numbers. If i need to observe physics quantities that are represented by the spherical harmonics coefficients which part should i look at- real part, complex part or the magnitudes (sqrt(real^2 + imaginary^2) of spherical harmonic coefficients?