perhatikan gambar disamping

Ketiga sudut tsb saling berpenyiku, maka:

AOB + BOC + COD = 90
3a + 2a + a = 90
6a = 90
a = 15

AOB = 3a = 3 . 15 = 45
BOC = 2a = 2 . 15 = 30
COD = a = 15