< AOB = α
\frac{l_2}{l_1}=\frac{2}{3}
l_2= \frac{\pi r\alpha }{180}
l_1= \frac{\pi r(360- \alpha ) }{180}
\frac{\pi r\alpha }{180}*\frac{180}{\pi r(360-\alpha)}=\frac{2}{3}
\frac{\alpha}{360-\alpha}=\frac{2}{3}
3\alpha=720-2\alpha
5\alpha=720 | / 5
\alpha=144 st
< APB = 180 - 144 = 36 st