If 0 ≤θ<π and the equation in (2sinθ)x^2-2x-cosθ=0 has two equal roots, find the value of θ.
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A.Maths(10 marks)!!
2006-10-15 6:38 pm
回答 (1)
2006-10-15 7:00 pm
✔ 最佳答案
If 0 ≤θ<π and the equation in (2sinθ)x2-2x-cosθ=0 has two equal roots, find the value of θ.有相等根所以判別式為零
B2 – 4AC = 0
(-2)2 – 4(2sinθ)( -cosθ) = 0
4 + 8sinθcosθ = 0
4 + 4sin2θ= 0
4sin2θ = -4
sin2θ = -1
2θ = 3π/2
θ = 3π/4
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