4sinθ - 3tanθ = 0, where 0˚≦θ < 360˚ (cor. to 1 d.p.)
ans: 0˚, 41.4˚, 180˚, 318.6˚
S.4 trigo(急急急)~
2010-05-15 5:36 pm
回答 (1)
2010-05-15 6:01 pm
✔ 最佳答案
4sinθ - 3tanθ = 0, where 0˚ <= θ < 360˚ (cor. to 1 d.p.)4sinθ – 3sinθ/cosθ = 0
4sinθcosθ – 3sinθ = 0
sinθ ( 4cosθ – 3 ) = 0
sinθ = 0 or 4cosθ – 3 = 0
When sinθ = 0
θ = 0˚ or 180˚
When 4cosθ – 3 = 0
cosθ = 3/4
θ = 41.4˚ or 318.6˚
Ans. : θ = 0˚, 41.4˚, 180˚, 318.6˚
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https://hk.answers.yahoo.com/question/index?qid=20100515000051KK00300