如图,点D、E、F分别是△ABC各边的中点,连接DE、EF、DF.若△ABC的周长为10,则△DEF的周长为____.
—Have you ever been to abroad as an exchange student(交换生)?
—No, I haven't.
如图,△ABC中,BO,CO分别是∠ABC,∠ACB的平分线,∠A=50°,则∠BOC等于( )