NB. NISHIKAWA Toshio JAPLA Oct. 2019 NB. Inversion of complex number NB. for J8 and later invert0 =: 3 : 0 'sx sy' =. y sx =. sx - X0 sy =. sy - Y0 if. sx >: 0 do. salph =. arctan(sy % sx) else. salph =. 1p1 - arctan((-sy) % sx) end. Len =. (*: R0) % (%: +/ *: sx, sy) Tx =. Len * cos salph Ty =. Len * sin salph Tx, Ty )