:: deftheorem Def14 defines Im2 QUATERNI:def 14 :
for z being Quaternion
for b₂ being Number holds
( ( z in COMPLEX implies ( b₂ = Im2 z iff b₂ = 0 ) ) & ( not z in COMPLEX implies ( b₂ = Im2 z iff ex f being Function of 4,REAL st
( z = f & b₂ = f . 2 ) ) ) );