We are now working closely together, p____(政治地) and economically.
化学是一门以实验为基础的学科。根据下图,回答问题。
①∠AOB+∠BOC=45。;② |BC| =2AB;
③ |OB|2 =10 |AB|2 ; ④ |OC|2 = 85|OB|2