complementary angles sums up to 90 degrees 1:9 is the division of the total angle that is 90 degrees. So the sum of ratios 1+9-10 Dividing total angle by total ratio: 90/10 9 Now its clear that each single ratio contains 9 degrees. so 1:9 means 9 x 1: 9 x 9 which means: 9:81
