下列各不等式中,0≤θ<2π。求θ值的範圍。
a 2sinθ≤1
b sin2θ+cosθ<0
更新1:
a 2sin²θ≤1
a-maths!!!!!
回答 (1)
2008-04-08 7:12 am
✔ 最佳答案
a 2sinθ≤1 sinθ ≤ 1/2
0≤θ≤π/6 or 5π/6 ≤θ< 2π
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b sin2θ+cosθ<0
2sinθcosθ + cosθ< 0
(2sinθ+ 1) cosθ< 0
(2sinθ+ 1) < 0 and cosθ> 0 or (2sinθ+ 1) > 0 and cosθ< 0
sinθ < -1/2 and cosθ> 0 or sinθ > -1/2 and cosθ< 0
3π/2 <θ≤ 11π/6 or π/2 <θ< 7π/6
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https://hk.answers.yahoo.com/question/index?qid=20080407000051KK03189