若cosθ=-
|
∵cosθ=-
，θ∈（π，2π），3 5
∴sinθ=-
2=-1-(-
)3 5 4 5
∴tanθ=
=sinθ cosθ 4 3
tanθ=
=2tan θ 2 1-tan2 θ 2 4 3
解得；tan
=-2或θ 2 1 2
∵θ∈（π，2π），
∈（θ 2
，π）π 2
∴tan
=-2θ 2
故选；A．
选择句子，补全对话，其中有两项是多余的。 A: Hi, Zhou Qiang. Haven’t seen you for too long! 小题1: B: I’ve just been to the Three Gorges (三峡). A: Really? 小题2: B: Right. As you know, we’ve built a great dam (坝) across the Changjiang River. A: 小题3: B: Yes, the dam is stopping water these days. And the water is rising 2 meters every day until it is 135 meters high. A: Oh, it’s said the beautiful scenery (风景) of Kuimen will be under water. What a pity! B: 小题4: It has been copied in another place with some other places of interest. A: Great！I want to go to the Three Gorges this summer. Would you like to go there with me again? B: I’d love to! 小题5:
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