suatu Δ ABC ,dengan sudut A=30° ,sudut C=120° dan panjang C=8cm . Maka panjang α adalah...cm

Gunakan aturan sinus

Rumus:
a/sinA = b/sinB = c/sinC

Diketahui:
c = 8 cm
sinA = 30°
sinC = 120°

Ditanya:
a = ??

Jawab:
a/sinA = c/sinC
a/sin30° = 8/sin120°
a/(1/2) = 8/(1/2√3)
a = (8 x 1/2)/(1/2√3)
a = 4/(1/2√3)
a = 8/√3 cm
a = 8/3 √3 cm