Trigonometry


  1. If π sinθ = 1, π cosθ = 1, then the value of 3tan
    2 θ
    + 1 is
    3










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    πsin θ = 1 and πcos θ = 1

    πsin θ
    = 1
    πcos θ

    ∴ tan θ = 1 = tan 45°
    ⇒ θ = 45°
    ∴ √3tan
    2 θ
    + 1
    3

    = √3tan
    2 × 45°
    + 1 = √3 tan30° + 1
    3

    Required answer = √3 ×
    1
    + 1 = 1 + 1 = 2
    3

    Correct Option: C

    πsin θ = 1 and πcos θ = 1

    πsin θ
    = 1
    πcos θ

    ∴ tan θ = 1 = tan 45°
    ⇒ θ = 45°
    ∴ √3tan
    2 θ
    + 1
    3

    = √3tan
    2 × 45°
    + 1 = √3 tan30° + 1
    3

    Required answer = √3 ×
    1
    + 1 = 1 + 1 = 2
    3


  1. Find the value of
    1
    +
    1
    .
    1 + tan2θ1 + cot2θ










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    Expression =
    1
    +
    1
    1 + tan2θ1 + cot2θ

    Expression =
    1
    +
    1
    sec2θcosec2θ

    [ ∵ sec2θ - tan2θ = 1 , cosec2θ - cot2θ = 1 ]
    Expression = cos2θ + sin2θ = 1
    [ ∵ cosθ . secθ = 1 , sinθ . cosecθ = 1 ]

    Correct Option: B

    Expression =
    1
    +
    1
    1 + tan2θ1 + cot2θ

    Expression =
    1
    +
    1
    sec2θcosec2θ

    [ ∵ sec2θ - tan2θ = 1 , cosec2θ - cot2θ = 1 ]
    Expression = cos2θ + sin2θ = 1
    [ ∵ cosθ . secθ = 1 , sinθ . cosecθ = 1 ]



  1. If tanθ +
    1
    = 2 , then the value of tan2θ +
    1
    is equal to :
    tanθtan2θ










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    tanθ +
    1
    = 2
    tanθ

    ⇒ tan2θ + 1 = 2tanθ
    ⇒ tan2θ - 2tanθ + 1 = 0
    ⇒ ( tanθ - 1 )2 = 0 ⇒ tanθ - 1 = 0
    ⇒ tanθ = 1
    ∴ tan2θ +
    1
    = 1 + 1 = 2
    tan2θ

    Correct Option: C

    tanθ +
    1
    = 2
    tanθ

    ⇒ tan2θ + 1 = 2tanθ
    ⇒ tan2θ - 2tanθ + 1 = 0
    ⇒ ( tanθ - 1 )2 = 0 ⇒ tanθ - 1 = 0
    ⇒ tanθ = 1
    ∴ tan2θ +
    1
    = 1 + 1 = 2
    tan2θ


  1. What is the value of
    (cotθ + cosecθ - 1)
    ?
    (cotθ - cosecθ + 1)










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    Expression =
    (cotθ + cosecθ - 1)
    (cotθ - cosecθ + 1)

    Expression =
    cotθ + cosecθ - (cosec2θ - cot2θ)
    (cotθ - cosecθ + 1)

    Expression =
    (cotθ + cosecθ) - (cosecθ - cotθ)(cosecθ + cotθ)
    (cotθ - cosecθ + 1)

    Expression =
    (cotθ + cosecθ)(1 - cosecθ + cotθ)
    = cotθ + cosecθ
    (cotθ - cosecθ + 1)

    Correct Option: A

    Expression =
    (cotθ + cosecθ - 1)
    (cotθ - cosecθ + 1)

    Expression =
    cotθ + cosecθ - (cosec2θ - cot2θ)
    (cotθ - cosecθ + 1)

    Expression =
    (cotθ + cosecθ) - (cosecθ - cotθ)(cosecθ + cotθ)
    (cotθ - cosecθ + 1)

    Expression =
    (cotθ + cosecθ)(1 - cosecθ + cotθ)
    = cotθ + cosecθ
    (cotθ - cosecθ + 1)



  1. If sinθ × cosθ =
    1
    .The value of sinθ – cosθ is where 0° < θ < 90°
    2










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    sinθ. cosθ =
    1
    2

    ⇒ 2 sinθ. cosθ = 1
    ⇒ sin2θ = 1 = sin 90°
    ⇒ 2θ = 90°
    ⇒ θ = 45°
    ∴ sinθ – cosθ = sin 45° – cos 45°
    sin 45° – cos 45° =
    1
    -
    1
    = 0
    22

    Correct Option: A

    sinθ. cosθ =
    1
    2

    ⇒ 2 sinθ. cosθ = 1
    ⇒ sin2θ = 1 = sin 90°
    ⇒ 2θ = 90°
    ⇒ θ = 45°
    ∴ sinθ – cosθ = sin 45° – cos 45°
    sin 45° – cos 45° =
    1
    -
    1
    = 0
    22