题目

The Future of Dairy Farming: Robot Milkers The future has arrived at a dairy(乳品的) farm in about an hour by car from WashingtonD.C. A robot is milking cows. It is milking time at Woodbourne Creamery in Mt. Airy, Maryland. The cows are standing in line for a turn at the robot. John Fendrick is the owner of the farm. He inspects the progress of the animals by looking at a computer screen. That is all he has to do.The door opens up, they walk in, and they get milked. The door opens up, and they walk out. The robot does all the work. It uses a laser to find each teat (乳头) — the pl已知点O为△ABC的外心，若∠A=80°，则∠BOC的度数为        .