Tom has three good friends. They are Jack, David and Mark. They have different hobbies. Tom likes football. He often plays football on weekends. He thinks playing football can make him strong and healthy. He is in the school football team.

    Jack doesn't like sports. He likes listening to music. He likes Jay Chow best of all the singers. He has many of his CDs. He often listens to music on the way. He thinks music can let him feel happy.

    David doesn't like sports or music. He likes stamps. He collects stamps for five years. The stamps are very beautiful. He thinks collecting stamps can help him know more about the world.

    Mark likes taking photos. He has a few cameras. When he is free, he often takes out his camera and takes some pictures. Some of his pictures are in the newspapers. He thinks the world is beautiful. He wants to show the beauty of the world to others.

如图，在平面直角坐标系中，点A的坐标是（1，1），如果将线段OA绕点O旋转135°，得线段OB，求点B的坐标？