Jawabanmu

2014-05-20T22:09:02+07:00
 \frac{AB}{sin C}  =  \frac{AC}{sin B}
 \frac{4}{sin 30} =  \frac{4 \sqrt{2} }{sin B}
4 sin B= 4  \sqrt{2} sin30
4 sin B = 4  \sqrt{2}  x  \frac{1}{2}
sin B =  \frac{2 \sqrt{2}}{4}
sin B =  \frac{1}{2}   \sqrt{2}
arc sin B = 120

A+B+C=180
A+120+30=180
A+150=180
A=180-150
A=30