Question

小魚

求過程

21413.
18
+11=45 - 18 = √27 = 3√3
)2. 已知tan=2且cos<0,則2sin-3cos日之值為何?
(A)-2
(B)√5
(B)學
(C)1
(D)2
(E) √5
LL
5
014
360

Answer 1

✨ 最佳解答 ✨

綾

tanθ = sinθ/cosθ = 2
=> sinθ = 2cosθ
(sinθ)^2 + (cosθ)^2 = 1
=> (2cosθ)^2 + (cosθ)^2 = 1
=> 5(cosθ)^2 = 1
=> cosθ = -1/(5^0.5) (cosθ < 0)
sinθ = -2/(5^0.5)
2sinθ - 3cosθ = cosθ = -1/(5^0.5)

小魚

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