[填空题]
The diagram below shows a tri+4e/w s5u+djy zt2rr 5dkk /jj1b 0hgxangular backyard ABC. A dog is on a lehcv,97nfjxqn lr5+ -gash attached to a pole at point A. The length of v 7r,ql5 ngx-jn+f9ch the leash is 10 metres.
1.Find the area of the backyard that the dog cannot reach. $m^2$
The owner of the dog estimates that the area the dog cannot reach is $50 m^2$.
2.Calculate the percentage error in the dog owner's estimate. %
