<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def chi_eff_from_spherical(mass1, mass2, spin1_a, spin1_polar, spin2_a, spin2_polar):
 """Returns the effective spin using spins in spherical coordinates."""

    spin1z = spin1_a * numpy.cos(spin1_polar)
    spin2z = spin2_a * numpy.cos(spin2_polar)
    return chi_eff(mass1, mass2, spin1z, spin2z)