____+45=____+55,这里运用了加法____,用字母表示是____.
已知△ABC的外接圆的圆心为O,半径为1,若3OA→+4OB→+5OC→=0→,则△AOC的面积为( )
关于北京气候特征的叙述,正确的是( )
如图,已知:点B、F、C、E在一条直线上,∠B=∠E,BF=CE,AB=DE.
求证:△ABC≌△DEF.
— How old is Mary?
— She is having her______ birthday this weekend.