有重要负荷的用户，在已取得供电企业供给的保安电源后，无需采取其他应急措施。
参考答案：错
Questions 11 to 18 are based on the conversation you have just heard.
A．Colin’s speech was more interesting than any other speakers’.
B．Colin’s speech was dull because it was too lengthy and tedious.
C．Colin’s speech wasn’t very good but he will do better next time.
D．Colin’s speech was good considering the difficulty of addressing so many audience.
面角恒等定律有什么条件？
