theorem :: QUATERN2:29

for r being Quaternion holds
( Rea (r ") = (Rea r) / (|.r.| ^2) & Im1 (r ") = - ((Im1 r) / (|.r.| ^2)) & Im2 (r ") = - ((Im2 r) / (|.r.| ^2)) & Im3 (r ") = - ((Im3 r) / (|.r.| ^2)) )