The minimum value of 2cosθ + 1sinθ&nbs

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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11.

The minimum value of 2cosθ + 1sinθ + 2tanθ in the interval 0, π2 is :

  • 2 + 2

  • 32

  • 23

  • 3 + 2


B.

32

Let y =2cosθ + 1sinθ + 2tanθdy = - 2sinθ - cscθcotθ + 2sec2θ= - 2sinθ - cosθsinθ . 1sinθ + 21cos2θ2sinθFor extremum, put dydx = 0 θ = π4Now, d2ydx2 = - 2cosθ - - csc3θ + cot2θcscθ                        + 2 2secθtanθsecθ                 = - 2cosθ + csc3θ - cot2θcscθ                         + 22sec2θtanθ                 > 0         for θ = π4 y is minimum for θ = π4. miny = 2 . 12 + 2 + 21                = 22 + 2 = 32


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12.

Let x1 and x2 be solutions of the equation sin-1x2 - 3x + 52 = π6. Then, the value of x12 + x22 is :

  • 4

  • 5

  • 52

  • 6


13.

If the derivative of the function f(x) is every where continuous and is given by

fx = bx2 + ax + 4; x  - 1ax2 + b;          x < - 1, then :

  • a = 2, b = - 3

  • a = 3, b = 2

  • a = - 2, b = - 3

  • a = - 3, b = - 2


14.

If f(x + y) = f(x)f(y) for all real x and y, f(6) = 3 and f'(0) = 10, then f'(6) is :

  • 30

  • 13

  • 10

  • 0


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15.

The value of determinant, 13 + 325515 + 265103 + 65155 is :

  • 56 - 5

  • 536 - 5

  • 56 - 3

  • 27 - 5


16.

Derivative of sec-111 - 2x2 w . r. t sin-13x - 4x3 is :

  • 14

  • 32

  • 1

  • 23


17.

Let D = {1, 2, 35, 6, 10, 15, 30}. Define the operattons '+', ' . ' and ' ' ' on D as follows a + b = LCM(a, b), a . b = GCD(a, b) and a' = 30a Then (15' + 6) · 10 1s equal to :

  • 1

  • 2

  • 3

  • 5


18.

a +xbcab +ycabc +z is equal to :

  • abc1 + xa + yb + zc

  • abc1 + ax + by + cz

  • xyz1 + ax + by + cz

  • xyz1 + xa + yb + zc


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19.

The solution of the differential equation xdydx + 2y = x2 is :

  • y = x2 + c4x2

  • y = x24 + c

  • y = x2 + cx2

  • y = x4 + c4x2


20.

y = - A cos(5x) + B sin(5x) satisfies the differential equation :

  • d2ydx2 + 10dydx + 25y = 0

  • d2ydx2 - 10dydx + 25y = 0

  • d2ydx2 - 25y = 0

  • d2ydx2 + 25y = 0


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