A:楚庄王想了解青铜鼎的铸造
B:楚庄王想借助周王室争霸
C:分封制受到挑战
D:楚庄王已与周王平起平坐
I will tell you a secret, but you must promise it around.
如图,在直角三角形ABC中,∠ACB=90°,D是AB上一点,且∠ACD=∠B.
求证:CD⊥AB.