[填空题]
Two concentric circles with centre O are shown in the dia* 4zm0i uojjxw:n* *27p eenoyma7)x ugr9(sj 9+ cdlyqyam below. The radius of the smaller circle is 5 cm and the radius of j+dc 99ysq( ylthe larger circle is 7 cm. Points A and B lie on the circumference of the larger circle such that 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. $cm^2$
