In the first figure angles (D and B) and (A and C) are both equal to each other and a quadrilateral must add up to 360 degrees, so angle (A and C) and (D and B) are supplementary angles. And angles g and f are complementary angles only if E = 90 degrees
In the first figure angles (D and B) and (A and C) are both equal to each other and a quadrilateral must add up to 360 degrees, so angle (A and C) and (D and B) are supplementary angles. And angles g and f are complementary angles only if E = 90 degrees