[填空题]
Two concentric circles with centre O arzeqsl.m kghcr:+; .fk9cy6/f e shown in the diagram below. The radius 9.rehcmgkq lf6s ;:y+fcz . k/dsg n;58 hluwjd(y )p)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 t8;pwsdlu (g ynj)5 dh)hat 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. $cm^2$
