Segitiga ABC dengan panjang BC = 3 cm, AC = 4 cm dan A. Cos B B. C. Panjang AB

Bab Trigonometri
Matematika SMA Kelas X

1] aturan sinus
AC/sin B = BC / sin A
4/sin B = 3 / sin 30°
Sin B = 1/2 . 4 /3
Sin B = 2/3

Cos B = √(1 - (2/3)²)
Cos B = 1/3 √5

B = 41,81°

2] sudut C = 180° - (30° + 41,81°)
Sudut C = 108,19°

3] AB/sin C = BC/sin A
AB = 3 . sin 108,19° / sin 30°
AB = 5,7 cm