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BITSAT2018MathematicsDeterminantsActual

If x 2 = sin θ cos θ 0 - cos θ sin θ 1 sin θ cos θ 2 then the value of 4 x 2 + x sin 3 π 2 + 5 is

Options

  1. A13 - 2
  2. B13 + 2
  3. C2 - 13
  4. DBoth (A) and (B)

Correct answer

D. Both (A) and (B)

Step-by-step solution

Given, x 2 = sin θ cos θ 0 - cos θ sin θ 1 sin θ cos θ 2 On expanding sin θ cos θ 0 - cos θ sin θ 1 sin θ cos θ 2 along C 3 , we get x 2 = 0 - 1 sin θ cos θ sin θ cos θ + 2 sin θ cos θ - cos θ sin θ = - 1 sin θ cos θ - sin θ cos θ + 2 sin 2 θ + cos 2 θ = - 1 × 0 + 2 × 1 ⇒ x 2 = 2 ⇒ x = ± 2 If x = 2 , then 4 x 2 + x sin 3 π 2 + 5 = 4 × 2 2 - 2 + 5 = 8

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