The longitude of Moon = ( m − P ∗ R s i n ( m − a ) 360 ) {\displaystyle \left(m-{\frac {P*Rsin(m-a)}{360}}\right)} – Surya Siddhanta II.39.43[1] where m is the Moon's mean longitude, a is the longitude at apogee, P is epicycle of apsis, R=3438'.