人的性别主要是由性染色体决定的，男性体细胞中的一对性染色体组成是____，女性体细胞中的一对性染色体组成是____。（用符号来表示）  

阅读理解

    Every country has its favourite food. In some countries, people(人们) eat rice every day. They often eat it with meat, fish and vegetables.       

   Japanese(日本人) eat a lot of fish, and they eat a lot of rice, too. In England(英国), the favourite food is fried fish and French fries. In the USA(美国) people like hamburgers a lot. And they like to have cold drinks. In Canada, people eat bread with butter(黄油) on it. In India, people like to eat hot food. Some people eat only fruit and vegetables. They don't like to eat meat and fish. They think green food is good for them.

cos（﹣510°）的值为（　　）