[填空题]
Two concentric circles with cena-3jg lwl jng p4:nr63tre O are shown in the dia(stn50wxytp6hh g 11kzf lc n.dxlxjv;5-0 1agram below. The radius of the smaller circle is 5 cm and the radius of the larger circle is 7 cm. Points A and B lie on the circumference of the larger circle such that5(hwkt5v zx6 s cfj;n1lltn1 a yx0hxd.g1p -0 angle $\mathrm{A}\hat{\mathrm{O}}\mathrm{B}$ is $\frac {\pi}{5}$ radians.
1.Find the length of the short arc AB. cm
2.Find the area of the shaded region. $cm^2$
