Perhatikan gambar berikut. Nilai sin sudut acb =

CD = √(6^2 - 4^2) = √(36 - 16) = √20 = 2√5
tan 30° = CD/DB
1/3 √3 = 2√5 / DB
√3 DB = 6√5

DB = 6√5/√3 . √3/√3 = 6√15/3 = 2√15
AC/(sin ABC) = AB/(sin ACB)
6/(sin 30°) = (4 + 2√15) / (sin ACB)
6/(1/2) = (4 + 2√15) / (sin ACB)
6 sin ACB = (2 + √15)
Sin ACB = (2 + √15)/6 = (1/6) (2 + √15)