[填空题]
The diagram below shows a triangular backyard ABC. A dog is on a le -k. e3ynr;4n,1 uh vmnmu-ykkash att 8n56atgg, wbr4s5naq ached to a pole at point A. The length of theg8g 5 n n46rsa5b,twqa 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. %
