theorem Th82: :: COMPLEX2:84

for a, b, c being Complex st a <> b & b <> c & 0 < angle (a,b,c) & angle (a,b,c) < PI holds
( ((angle (a,b,c)) + (angle (b,c,a))) + (angle (c,a,b)) = PI & 0 < angle (b,c,a) & 0 < angle (c,a,b) )