Q7 / 40 · NTA Abhyas (JEE Main) 2020 · Mathematics · Hyperbola

If the eccentricity of the hyperbola x21+sin⁡θ2-y2cos2⁡θ=1 is 23, then the sum of all the possible values of θ is (where, θ∈0,π)

  • A
    5π4
  • B
    2π3
  • C
    7π4
  • Correct answer
    D
    π

Solution

e2=1+cos2⁡θ1+sin⁡θ2=43⇒cos2⁡θ1+sin⁡θ2=13
⇒cos⁡θ1+sin⁡θ2=13⇒sin⁡π2-θ1+cos⁡π2-θ2=13
⇒tan2⁡π4-θ2=13
π4-θ2=-π6,π6⇒θ2=π4-π6,π4+π6
θ=π2±π3=π6,5π6

Hence, the required sum =π

Hence, the correct answer is option: 'D'.

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