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Public Exam Model Question Paper III 2019 - 2020

12th Standard

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Maths

Time : 02:45:00 Hrs
Total Marks : 90

    Part I

    Answer all the questions.

    Choose the most suitable answer from the given four alternatives and write the option code with the corresponding answer.

    20 x 1 = 20
  1. If 0 ≤ θ  ≤ π and the system of equations x + (sinθ)y - (cosθ)z = 0, (cosθ)x - y +z = 0, (sinθ)x + y - z = 0 has a non-trivial solution then θ is

    (a)

    \(\frac { 2\pi }{ 3 } \)

    (b)

    \(\frac { 3\pi }{ 4 } \)

    (c)

    \(\frac { 5\pi }{ 6 } \)

    (d)

    \(\frac { \pi }{ 4 } \)

  2. If A = [2 0 1] then the rank of AAT is ______

    (a)

    1

    (b)

    2

    (c)

    3

    (d)

    0

  3. If a = cos θ + i sin θ, then \(\frac { 1+a }{ 1-a } \) = ___________

    (a)

    cot \(\frac { \theta }{ 2 } \)

    (b)

    cot θ

    (c)

    i cot \(\frac { \theta }{ 2 } \)

    (d)

    i tan\(\frac { \theta }{ 2 } \)

  4. If f and g are polynomials of degrees m and n respectively, and if h(x) = (f g)(x), then the degree of h is

    (a)

    mn

    (b)

    m+n

    (c)

    mn

    (d)

    nm

  5. If ax2 + bx + c = 0, a, b, c \(\in\) R has no real zeros, and if a + b + c < 0, then __________

    (a)

    c>0

    (b)

    c<0

    (c)

    c=0

    (d)

    c≥0

  6. The equation \(\tan ^{-1} x-\cot ^{-1} x=\tan ^{-1}\left(\frac{1}{\sqrt{3}}\right)\)has

    (a)

    no solution

    (b)

    unique solution

    (c)

    two solutions

    (d)

    infinite number of solutions

  7. If \({ sin }^{ -1 }x-cos^{ -1 }x=\frac { \pi }{ 6 } \) then ___________

    (a)

    \(\frac { 1 }{ 2 } \)

    (b)

    \(\frac { \sqrt { 3 } }{ 2 } \)

    (c)

    \(\frac { -1 }{ 2 } \)

    (d)

    none of these

  8. The eccentricity of the ellipse (x−3)2 +(y−4)2 \(=\frac { { y }^{ 2 } }{ 9 } \) is

    (a)

    \(\frac { \sqrt { 3 } }{ 2 } \)

    (b)

    \(\frac { 1 }{ 3 } \)

    (c)

    \(\frac { 1 }{ 3\sqrt { 2 } } \)

    (d)

    \(\frac { 1 }{ \sqrt { 3 } } \)

  9. The angle between the lines \(\frac{x-2}{3}=\frac{y+1}{-2}, z=2 \text { and } \frac{x-1}{1}=\frac{2 y+3}{3}=\frac{z+5}{2}\) is

    (a)

    \(\frac{\pi}{6}\)

    (b)

    \(\frac{\pi}{4}\)

    (c)

    \(\frac{\pi}{3}\)

    (d)

    \(\frac{\pi}{2}\)

  10. The point of inflection of the curve y = (x - 1)3 is

    (a)

    (0, 0)

    (b)

    (0, 1)

    (c)

    (1, 0)

    (d)

    (1, 1)

  11. \(\underset { x\rightarrow 0 }{ lim } \frac { x }{ tanx } \) is _________

    (a)

    1

    (b)

    -1

    (c)

    0

    (d)

  12. Linear approximation for g(x) = cos x at \(x=\frac{\pi}{2}\) is

    (a)

    \(x+\frac{\pi}{2}\)

    (b)

    \(-x +\frac{\pi}{2}\)

    (c)

    \(x - \frac{\pi}{2}\)

    (d)

    \(-x - \frac{\pi}{2}\)

  13. If the radius of the sphere is measured as 9 cm with an error of 0.03 cm, the approximate error in calculating its volume is _____________

    (a)

    9.72 cm3

    (b)

    0.972 cm3

    (c)

    0.972π cm3

    (d)

    9.72π cm3

  14. The value of \(\int _{ -4 }^{ 4 }{ \left[ { tan }^{ -1 }\left( \frac { { x }^{ 2 } }{ { x }^{ 4 }+1 } \right) +{ tan }^{ -1 }\left( \frac { { x }^{ 4 }+1 }{ { x }^{ 2 } } \right) \right] dx } \) is

    (a)

    \(\pi\)

    (b)

    \(2\pi\)

    (c)

    \(3\pi\)

    (d)

    \(4\pi\)

  15. The value of \(\int _{ 0 }^{ \frac { \pi }{ 3 } } { tan } x \ dx\) __________

    (a)

    -log 2

    (b)

    log 2

    (c)

    -log 3

    (d)

    log 3

  16. The integrating factor of the differential equation \(\frac{d y}{d x}+P(x) y=Q(x)\) is x, then P(x)

    (a)

    x

    (b)

    \(\frac { { x }^{ 2 } }{ 2 } \)

    (c)

    \(\frac{1}{x}\)

    (d)

    \(\frac{1}{x^2}\)

  17. The differential equation associated with the family of concentric circles having their centres at the origin is _________.

    (a)

    \(\frac { dy }{ dx } =\frac { -x }{ y } \)

    (b)

    \(\frac { dy }{ dx } =\frac { -y }{ x } \)

    (c)

    \(\frac { dy }{ dx } =\frac { x }{ y } \)

    (d)

    \(\frac { dy }{ dx } =\frac { y }{ x } \)

  18. If the function \(f(x)=\frac { 1 }{ 12 } \) for a < x < b, represents a probability density function of a continuous random variable X, then which of the following cannot be the value of a and b?

    (a)

    0 and 12

    (b)

    5 and 17

    (c)

    7 and 19

    (d)

    16 and 24

  19. Determine the truth value of each of the following statements:
    (a) 4 + 2 = 5 and 6 + 3 = 9
    (b) 3 + 2 = 5 and 6 + 1 = 7
    (c) 4 + 5 = 9 and 1 + 2 = 4
    (d) 3 + 2 = 5 and 4 + 7 = 11

    (a)
    (a) (b) (c) (d)
    F T F T
    (b)
    (a) (b) (c) (d)
    T F T F
    (c)
    (a) (b) (c) (d)
    T T F F
    (d)
    (a) (b) (c) (d)
    F F T T
  20. The identity element in the group {R - {1},x} where a * b = a + b - ab is __________

    (a)

    0

    (b)

    1

    (c)

    \(\frac { 1 }{ a-1 } \)

    (d)

    \(\frac { a }{ a-1 } \)

  21. Part II

    Answer any 7 questions. Question no. 30 is compulsory.

    10 x 2 = 20
  22. Find the rank of the matrix A =\(\left[ \begin{matrix} 4 \\ 7 \end{matrix}\begin{matrix} 5 \\ -3 \end{matrix}\begin{matrix} -6 \\ 0 \end{matrix}\begin{matrix} 1 \\ 8 \end{matrix} \right] \).

  23. Find the Interval for a for which 3x2+2(a2+1) x+(a2-3a+2) possesses roots of opposite sign.

  24. Find the locus of a point which divides so that the sum of its distances from (-4, 0) and (4, 0) is 10 units.

  25. Find the acute angle between the following lines
    2x = 3y = −z and 6x = − y = −4z.

  26. Determine the domain of convexity of the function y=ex

  27. If w(x, y, z) = x2 y + y2z + z2x, x, y, z∈R, find the differential dw .

  28. Find the area of the region enclosed by the curve y = \(\sqrt x\) + 1, the axis of x and the lines x = 0, x = 4.

  29. Solve the Linear differential equation:
    \(\frac { dy }{ dx } =\frac { { sin }^{ 2 }x }{ 1+{ x }^{ 3 } } -\frac { { 3x }^{ 2 } }{ 1+{ x }^{ 3 } } y\)

  30. A commuter train arrives punctually at a station every half hour. Each morning, a student leaves his house to the train station.Let X denote- the amount of time, in minutes that the student waits for the train from the time he reaches the train station. It is known  that the pdf of X is 
    \(f(x)= \begin{cases}\frac{1}{30} & 0

  31. Part III

    Answer any 7 questions. Question no. 40 is compulsory.

    10 x 3 = 30
  32. For what value of t will the system tx +3y - z = 1, x + 2y + z = 2, -tx + y + 2z = -1 fail to have unique solution?

  33. Simplify the following:
    i 1729

  34. If α, β and γ are the roots of the cubic equation x3+2x2+3x+4 = 0, form a cubic equation whose roots are, 2α, 2β, 2γ

  35. Solve: (x-1)4+(x-5)= 82

  36. Solve: \({ tan }^{ -1 }\left( \cfrac { x-1 }{ x-2 } \right) +{ tan }^{ -1 }\left( \cfrac { x+1 }{ x+2 } \right) =\cfrac { \pi }{ 4 } \)

  37. Identify the type of the conic for the following equations:
    (1) 16y= −4x2+64
    (2) x2+y= −4x−y+4
    (3) x2−2y = x+3
    (4) 4x2−9y2−16x+18y−29 = 0

  38. If \(\overset { \rightarrow }{ a } =\overset { \wedge }{ i } -\overset { \wedge }{ j } ,\overset { \rightarrow }{ b } =\overset { \wedge }{ j } -\overset { \wedge }{ k } ,\overset { \rightarrow }{ c } =\overset { \wedge }{ k } -\overset { \wedge }{ i } \) then find \(\left[ \overset { \rightarrow }{ a } -\overset { \rightarrow }{ b } ,\overset { \rightarrow }{ b } -\overset { \rightarrow }{ c } ,\overset { \rightarrow }{ c } -\overset { \rightarrow }{ a } \right] \)

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    parametric form od vector equation

  39. Compute the value of 'c' satisfied by Rolle’s theorem for the function \(f(x)=log(\frac{x^{2}+6}{5x})\) in the interval [2, 3]

  40. Part IV

    Answer all the questions.

    14 x 5 = 70
  41. Write the function \(f(x)=\tan ^{-1} \sqrt{\frac{a-x}{a+x}}-a<x<a \) in the simplest form

  42. The foci of a hyperbola coincides with the foci of the ellipse \(\frac { { x }^{ 2 } }{ 25 } +\frac { y^{ 2 } }{ 9 } =1\). Find the equation of the hyperbola if its eccentricity is 2.

  43. If \(\left| \overset { \rightarrow }{ A } \right| =\overset { \wedge }{ i } +\overset { \wedge }{ j } +\overset { \wedge }{ k } \) and \(\overset { \wedge }{ i } =\overset { \wedge }{ j } -\overset { \wedge }{ k } \) are two given vector, then find a vector B satisfying the equations \(\overset { \rightarrow }{ A } \times \overset { \rightarrow }{ B } \)\(\overset { \rightarrow }{ C } \) and \(\overset { \rightarrow }{ A } \).\(\overset { \rightarrow }{ B } \) = 3

  44. Using the l’Hôpital Rule prove that, \(\underset{x\rightarrow 0^{+}}{lim}(1+x)^{\frac{1}{x}}=e\)

  45. Prove that f(x, y) = x3 - 2x2y + 3xy2 + y3 is homogeneous; what is the degree? Verify Euler's Theorem for f.

  46. Find the area of the region common to the circle x2+y2=16 and the parabola y2=6x.

  47. The equation of electromotive force for an electric circuit containing resistance and self inductance is E = Ri + L\(\frac{di}{dt},\) Where E is the electromotive force is given to the circuit, R the resistance and L, the coefficient of induction. Find the current i at time t when E = 0.

  48. Sovle \(\left( x+2 \right) \frac { dy }{ dx } =x2+4x-9\) .Also find the domain of the function.

    1. If X is the random variable with distribution function F(x) given by,

      then find (i) the probability density function f(x) 
      (ii) P(0.3 ≤ X ≤ 0.6)

    2. For what value of λ, the system of equations x + y + z = 1, x + 2y + 4z = λ, x + 4y + 10z = λ2 is consistent.

    1. Show that \(\left( \frac { i+\sqrt { 3 } }{ -i+\sqrt { 3 } } \right) ^{ 2\omega }+\left( \frac { i-\sqrt { 3 } }{ i+\sqrt { 3 } } \right) ^{ 2\omega }\) = -1

    2. Solve the equation (x-2) (x-7) (x-3) (x+2)+19 = 0

    1. Find the principal value of
      sec−1(−2).

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