Q33 / 90 · JEE Main 2017 (08 Apr Online) · Mathematics

If two parallel chords of a circle, having diameter 4 units, lie on the opposite sides of the center and subtend angles cos-1⁡17 and sec-1⁡7 at the center respectively, then the distance between these chords is:

  • Correct answer
    A
    87
  • B
    167
  • C
    47
  • D
    87

Solution

Given condition, 

Figure

∴ cos⁡2θ=17 ⇒2cos2θ-1=17

⇒2cos2⁡θ=87

⇒cosθ=27

Then, CP1=rcosθ=47

Since, cos−117=sec−17, hence both the chords are at equal distance from center of the circle.

Hence, the distance between the chords =2 × 4 7 = 8 7 .

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

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