Jawabanmu

2014-02-17T19:39:41+07:00
2/5 x 360° = 144°

144° : 180° = 4/5 rad 
1 4 1
2014-02-17T19:41:59+07:00
 \frac{2}{5} x 60 derajat = 12 derajat
radian = 12 x \frac{π}{180}
         =   \frac{π}{15} radian