如图,已知△ABC,请你按要求用尺规作出下列图形(不写作法,但要保留作图痕迹). (1)作出∠ABC的平分线BD;
(2)作出BC边上的垂直平分线EF.
解:
(1)
(2)
As is known, it was Hu Jintao, _____ president of our nation, who gave _____ lecture at the ceremony
of National Day[ ]
A. the; a
B. the ; /
C. a; the
D. /; a
反馈控制的实质是一个按( )控制的过程。
A.控制量 B.控制器 C.偏差 D.被控量