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![1/2](/uploads/image/z/2444093-53-3.jpg?t=1%2F2)
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1/2
1/2
1/2
角x在第一或第四象限.
2k派+派/6
由题知,
1/2< cosx <= √3/2
则
x∈(-π/3+2kπ,-π/6+2kπ]∪[π/6+2kπ,π/3+2kπ) ,
其中,k∈Z
希望采纳~~~
30
cos(±30)=根号3/2,cos(±60)=1/2
则x∈(-π/3+2kπ,-π/6+2kπ]∪[π/6+2kπ,π/3+2kπ) ,k∈Z