Number of solution(s) of the equation sin 2θ+cos2θ=−12,θ∈0,π2, is
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a
0
b
1
c
2
d
3
answer is B.
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Detailed Solution
Given that sin2θ+cos2θ=−12⇒2tanθ1+tan2θ+1−tan2θ1+tan2θ=−12⇒2tanθ+1−tan2θ1+tan2θ=−12⇒tan2θ−4tanθ−3=0 It is a quadratic equation in terms of tanθ⇒tanθ=4±16+122 ∵tanθ=−b±b2−4ac2a⇒tanθ=2±7 Number of solution of the given equation is 1 since tanθ is positive