①垂直于同一平面的所有向量一定共面；

②在△ABC中，已知 $\frac{\cos A}{a}=\frac{\cos B}{b}=\frac{\cos C}{c}$ ，则∠A=60°；

③在△ABC中，sin²A=sin²B+sin²C+sinBsinC，则A= $\frac{\pi }{3}$

④若a＞0，b＞0，a+b=2，则a²+b²≥2；

正确的序号有____．

阅读理解

    Mahatma Gandhi once said, “The greatness of a nation can be judged by the way its animals are treated.”

    There is no doubt that China is a country with high moral values. It has never attacked another country, has one of the lowest rates of violent crimes and is deeply concerned with the social and economic welfare of its people.

    But when it comes to animal rights, China may well fail Gandhi test. There are no laws against the killing of dogs and the sale of dog meat in China. In fact the serving of dog meat in Chinese restaurants has increased in recent years.

    People who eat dog meat argue that dogs have been eaten in China for thousand of years and dog meat has “health benefits”.

    There is, however, a strong argument against waiting dogs .Recently, some Chinese animal rights activists stopped a truck carrying about 500 dogs and saved the poor animals from being sold and served as food in restaurants. These people that dogs are not meant to be eaten but loved.

根据短文内容，判断以下句子的正误。