Let −π6<θ<−π12. Suppose α1 and β1 are the roots of the equation x2−2xsecθ+1=0, α2 and β2are the roots of the equation x2+2xtanθ−1=0. If α1>β1 and α2>β2, then α1+β2 equals
A
2(secθ−tanθ)
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B
2secθ
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C
−2tanθ
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D
\N
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Solution
The correct option is C−2tanθ Here,x2−2xsecθ+1=0 has roots α1 and β1. ∴α1,β1=2secθ±√4sec2θ−42×1=2secθ±2|tanθ|2
Since, θ∈(−π6,−π12),
i.e. θ∈IV quadrant =2secθ∓2tanθ2 α1=secθ−tanθ and β1=secθ+tanθ [as α1>β1] and x2+2xtanθ−1=0 has roots α2 and β2.
i.e. α2.β2=−2tanθ±√4tan2θ+42
and ∴α2=−tanθ+secθ β2=−tanθ−secθ[asα2>β2]
Thus, α1+β2=−2tanθ