theorem Th83: :: COMPLEX2:85

for a, b, c being Complex st a <> b & b <> c & angle (a,b,c) > PI holds
( ((angle (a,b,c)) + (angle (b,c,a))) + (angle (c,a,b)) = 5 * PI & angle (b,c,a) > PI & angle (c,a,b) > PI )