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Introduction to Trigonometry Test - 6

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Introduction to Trigonometry Test - 6
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  • Question 1
    1 / -0
    Find the value of .
    Solution
  • Question 2
    1 / -0
    If cosθ = 2cos2θ , then 2sec2θ – cos2θ + tan2θ =
    Solution
    cosθ = 2 cos2θ


    secθ = 2
    secθ = sec 60°
    θ = 60°
    2 sec2θ – cos2θ + tan2θ= 2 sec2 60° - cos2 60° + tan2 60° =
    =
    =
  • Question 3
    1 / -0
    is equal to
    Solution


    =

    =

    =

    = secθ.cotθ
  • Question 4
    1 / -0
    If xcotθ - ycosecθ = a and xcosecθ - ycotθ = b, then (y2 - x2)2 is equal to
    Solution
    xcotθ – ycosecθ = a
    Squaring both sides, we get
    x2cot2θ + y2cosec2θ – 2.xy.cotθ.cosecθ = a2 --- (1)
    xcosecθ – ycotθ = b
    Squaring both sides, we get
    x2cosec2θ + y2cot2θ – 2.xy.cosecθ.cotθ = b2 --- (2)
    Subtracting (2) from (1), we get
    x2cot2θ + y2cosec2θ – 2.xy.cotθ.cosecθ - (x2cosec2θ + y2cot2θ – 2.xy.cosecθ.cotθ) = a2 - b2
    x2cot2θ + y2cosec2θ - x2cosec2θ - y2cot2θ = a2 - b2
    cosec2θ(y2 – x2) – cot2θ(y2 – x2) = a2 – b2
    (y2 – x2)(cosec2θ – cot2θ) = a2 – b2
    (y2 – x2) = a2 – b2
    Squaring both sides,
    (y2 – x2)2 = (a2 - b2)2
  • Question 5
    1 / -0
    Simplify
    Solution


    =

    =

    =

    =

    =
  • Question 6
    1 / -0
    If tan A + cot A = 4, then what is the value of tan3 A + cot3 A?
    Solution
    According to the question,
    (a + b)3 = a3 + b3 + 3ab (a + b)
    ∴ a3 + b3 = (a + b)3 - 3ab (a + b)
    So, tan3 A + cot3 A = (tan A + cot A)3 - 3 . tan A . cot A (tan A + cot A)
    = (4)3 - 3 × 4
    = 64 - 12 = 52
  • Question 7
    1 / -0
    If , then equals
    Solution


    =

    =

    =

    =

    =

    =

    =
  • Question 8
    1 / -0
    If x + y = 90°, then what is the value of ?
    Solution
    ( x + y = 90°, Given)

    =

    =

    =
  • Question 9
    1 / -0
    If A + B = 90°, sin A = and cos B = , find the relation between p, q, r and s.
    Solution
    A + B = 90°
    B = 90° - A
    sin A = ……..(1)
    cos B =
    cos (90° - A) =
    sin A = ……..(2)
    From (1) and (2)
    = ps = rq
    Option (1) is correct.
  • Question 10
    1 / -0
    In triangle RPS, it is given that ∠P = 90° and cosecR = . Find the value of [tanS.cotR – secR.sinR + cosR]3.
    Solution
    cosecR = .

    cosec R = cosec 45°
    R = 45°
    P = 90°
    So, S = 45°
    [tanS.cotR – secR.sinR + cosR]3
    = (tan 45° cot 45° - sec45° sin45° + cos45°)3
    =
    =
    =
  • Question 11
    1 / -0
    If sin x + sin2 x = 1, then find the value of cos4 x + cos8 x + 2 cos6 x + 1.
    Solution
    sin x = 1 - sin2 x = cos2 x
    cos4 x + cos8 x + 2cos6 x + 1
    = sin2 x + sin4 x + 2 sin3 x + 1
    = (sin x + sin2 x)2 + 1
    = 2
  • Question 12
    1 / -0
    Evaluate: 21 cot48° cot81° cot42° cot9° - 9()3 + 16()2
    Solution
    21 cot48° cot81° cot42° cot9° - 9()3 + 16()2

    = 21 cot(90° - 42°) cot(90° - 9°) cot42° cot9° - 9()3 + 16()2

    = 21 tan42° tan9° cot42° cot9° - 9()3 + 16()2 [As cot(90° - θ) = tanθ, sec(90° - θ) = cosecθ, sin(90° - θ) = cosθ]

    = 21cot42° cot9° - 9(1)3 + 16(1)2

    = 21 – 9 + 16 = 12 + 16 = 28
  • Question 13
    1 / -0
    What is the value of q if cot(p + q – r + s) = 0, sin(p – q) = , cosec(q + s) = and sec(q + r) = 1?
    Solution
    cot(p + q – r + s) = 0
    cot(p + q – r + s) = cot 90°
    Therefore, (p + q – r + s) = 90° --- (1)
    Now, sin(p – q) =

    sin(p – q) = sin 30°
    So,(p – q) = 30° --- (2)
    Also, cosec(q + s) =
    cosec(q + s) = cosec 45°
    (q + s) = 45° --- (3)
    And sec(q + r) = 1
    sec(q + r) = sec 0°
    (q + r) = 0° --- (4)
    Now, adding equations (2) and (4),
    p + r = 30° --- (5)
    Now, putting (3) in (1),
    So, p – r = 90° - 45° = 45° --- (6)
    Now, subtracting equation (6) from equation (5),
    2r = -15°
    r = -7.5°
    Now, putting r = -7.5° in equation (4), we get
    q = 7.5°
  • Question 14
    1 / -0
    If cosθ =sinθ, then the value of+is
    Solution
    Gievn: cosθ =sinθ
    = --- (1)

    Now, +

    Dividing both numerator and denominator by sinθ,

    = +

    = + [From (1)]

    = +

    = +

    =

    = =
  • Question 15
    1 / -0
    What is the value of p in the following equation?

    p – sec4θ – cosec4θ = 2(tanθ + cotθ)2 - (sec2θ + cosec2θ)2
    Solution
    R.H.S.
    2(tanθ + cotθ)2- (sec2θ + cosec2θ)2

    = 2- (sec4θ + cosec4θ + 2 sec2θcosec2θ)

    = 2()2 - (sec4θ + cosec4θ + 2 sec2θcosec2θ)

    = 2sec2θcosec2θ - sec4θ - cosec4θ - 2sec2θcosec2θ

    = -sec4θ – cosec4θ

    Comparing this with L.H.S, we get

    p = 0
  • Question 16
    1 / -0
    What is the value of ?
    Solution

    Therefore, option (1) is correct.
  • Question 17
    1 / -0
    What is the value of ?
    Solution
    Given:

    =

    =

    =

    =

    =

    =
  • Question 18
    1 / -0
    =
    Solution


    =

    =

    = [As ]

    =
  • Question 19
    1 / -0
    If sin A + cosec A = 3, then find the value of .
    Solution
    sin A + cosec A = 3
    sin A + = 3

    Squaring both sides:
    sin2 A + + 2 = 9
    = 9 - 2 = 7
  • Question 20
    1 / -0
    What is the value of if ?
    Solution


    Squaring both sides,





    [As ]






  • Question 21
    1 / -0
    Which of the following statements is/are false?

    (A) If secθ + cosecθ = 1, then .

    (B).
    Solution
    (A) secθ + cosecθ = 1 --- (1)

    L.H.S. =

    =

    =

    = cotθ + secθ.tanθ + tanθ.cosecθ
    = cotθ + tanθ(secθ + cosecθ)
    = cotθ + tanθ [Using 1]

    =

    =

    Multiply numerator and denominator by 2

    =

    =

    =

    Therefore, L.H.S. is not equal to R.H.S.
    Hence, statement (A) is false.

    (B) R.H.S. =

    =

    =

    = sinR + secR
    Therefore, L.H.S. is not equal to R.H.S.
    Hence, statement (B) is false.
  • Question 22
    1 / -0
    Which of the following statements is/are CORRECT?

    (I) is dependent on θ.

    (II) .
    Solution


    Hence, statement I is correct as it is dependent on θ.

    (II) R.H.S. =



    =

    =

    =

    =

    = sin2θ – cosθ

    Therefore, L.H.S. is not equal to R.H.S.
    Hence, statement II is incorrect.
  • Question 23
    1 / -0
    If 4 cos2 A + 2 sin2 A = 3, then what is the value of A, given that A lies in the first quadrant?
    Solution
    4 cos2 A + 2 (1 - cos2 A) = 3

    4 cos2 A + 2 - 2cos2A = 3

    2 + 2 cos2A = 3

    2(1 + cos2 A) = 3
    1 + cos2 A =
    cos2 A = – 1
    =
    =

    cosA =
    A = 45°
  • Question 24
    1 / -0
    What is the value of x2 - 4 - y2 +if x = secθ – cosecθ and y = tanθ – cotθ?
    Solution
    x2 – 4 - y2 +

    After putting the values of x and y, the expression becomes:

    (secθ – cosecθ)2 – 4 – (tanθ – cotθ)2 +
    = (sec2θ + cosec2θ - 2secθ cosecθ) - 4 - (tan2θ + cot2θ - 2tanθ cot θ) +

    = sec2θ + cosec2θ - 2secθ cosecθ – 4 - tan2θ - cot2θ + 2tanθ cot θ +
    = 1 + 1 -- 4 + 2 cotθ +[As sec2θ - tan2θ = 1 and cosec2θ - cot2θ = 1]

    Now, 2 -- 2 +

    =
  • Question 25
    1 / -0
    Fill in the blanks:

    (i) If sec4θ + sec2θ = 1, then the value of 3 tan2θ + tan4θ is ____________.
    (ii) The value of+, if p = m tan6θ and q = n cot6θ, is ___________.
    (iii) If o = g cosecθ, m = gcotθ and n = Isecθ, then the value of o2– m2– n2+ I2tan2θ is ________.
    Solution
    (i) sec4θ + sec2θ = 1 [Given]
    sec2θ = 1 - sec4θ
    1 + tan2θ = 1 – (1 + tan2θ)2 [As sec2θ = 1 + tan2θ]
    1 + tan2θ = 1 – [1 + tan4θ + 2tan2θ]
    1 + tan2θ = 1 – 1 - tan4θ – 2tan2θ
    1 + 3tan2θ + tan4θ = 0
    3tan2θ + tan4θ = -1

    (ii) +
    Putting the values of p and q in this expression,

    +

    = tanθ + cotθ

    = +

    =

    = [As sin2θ + cos2θ = 1]

    (iii) o2– m2– n2+ I2tan2θ
    Putting the values of o, m and n in this expression,
    = g2cosec2θ - g2cot2θ - I2sec2θ + I2tan2θ
    = g2(cosec2θ - cot2θ) - I2(sec2θ - tan2θ)
    = g2- I2 [As cosec2θ - cot2θ = 1 and sec2θ - tan2θ = 1]
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