A:did he injure
B:injured him
C:was he injured
D:he was injured
△ABC是一个任意三角形,用直尺和圆规作出∠A、∠B的平分线,如果两条平分线交于点O,那么下列选项中不正确的是( )
若三棱锥的一条棱长为x,其余棱长均为1,体积是V(x),则函数V(x)在其定义域上为( )
如图,已知正五边形ABCDE,AF∥CD,交DB的延长线于点F,则∠DFA=____度.