let a, b, d, e be Complex; :: thesis: ((a + b) + e) / d = ((a / d) + (b / d)) + (e / d)
thus ((a + b) + e) / d = ((a + b) / d) + (e / d) by Th62
.= ((a / d) + (b / d)) + (e / d) by Th62 ; :: thesis: verum