The solution of tan-1x + 2cot-1x = 2π

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 Multiple Choice QuestionsMultiple Choice Questions

111.

If cos-1p +cos-1q +cos-1r = π, then p2 + q2 + r2 + 2pqr is equal to

  • 3

  • 1

  • 2

  • - 1


112.

If sin-1x5 +csc-154  = π2, then x is equal to

  • 1

  • 4

  • 3

  • 5


113.

sin12cos-145

  • - 110

  • 110

  • - 110

  • 110


114.

If cos-1x + cos-1y + cos-1z = 3π, then xy + yz + zx is equal to

  • 1

  • 0

  • - 3

  • 3


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115.

If tan-1x + 1x - 1 + tan-1x - 1x = tan-1- 7, then the value of x is

  • zero

  • - 2

  • 1

  • 2


116.

If cos-1p + cos-11 - p +cos-11 - q = 3π4, then the value of q is

  • 22

  • 1

  • 1/2

  • 1/3


117.

The soluton of sin-1x - sin-12x = ± π3 is

  • ± 13

  • ± 14

  • ± 32

  • ± 12


118.

If cos-1x = α, 0 < x < 1 and sin-12x1 - x2 + sec-112x2 - 1 = 2π3, then tan-12x equals :

  • π6

  • π4

  • π3

  • π2


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119.

If a > b > 0, then the value of tan-1ab + tan-1a + ba - b depends on :

  • both a and b

  • b and not a

  • a and not b

  • neither a nor b


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120.

The solution of tan-1x + 2cot-1x = 2π3 is

  • - 13

  • 13

  • - 3

  • 3


D.

3

We have, tan-1x + 2cot-1x = 2π3                tan-1x + 2tan-11x = 2π3 tan-1x + tan-121x1 - 1x2 = 2π3           2tan-1x = tan-12x1 - x2 tan-1x + 2xx2 - 11 - 2xx2 - 1 = tan2π3           x3 - x + 2xx2 - 1 - 2x2 = tan2π3                  x3 + x- 1 - x2 = tan2π3               xx2 + 1- 1x2 + 1 = - 3                                x = 3


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