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Differentials and Partial Derivatives 2 Mark Book Back Question Paper With Answer Key

12th Standard

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Maths

Time : 00:30:00 Hrs
Total Marks : 68

    2 Marks

    34 x 2 = 68
  1. Use the linear approximation to find approximate values of \({ (123) }^{ \frac { 2 }{ 3 } }\)

  2. Use the linear approximation to find approximate values of \(\sqrt [ 4 ]{ 15 } \)

  3. Use the linear approximation to find approximate values of \(\sqrt [ 3 ]{ 26 } \)

  4. Let g(x) = x2 + sin x. Calculate the differential dg.

  5. Find differential dy for each of the following function \(y=\frac { { \left( 1-2x \right) }^{ 3 } }{ 3-4x } \)

  6. Find differential dy for each of the following function
    y = (3 + sin(2x)) 2/3 

  7. Find differential dy for each of the following function
    y = ex2-5x+7 cos (x2 - 1)

  8. Consider g(x,y) = \(\frac { 2{ x }^{ 2 }y }{ { x }^{ 2 }+{ y }^{ 2 } } \), if (x, y) ≠ (0, 0) and g(0, 0) = 0 Show that g is continuous on R2

  9. Let f (x, y) = 0 if xy ≠ 0 and f (x, y) = 1 if xy = 0.
    Calculate: \(\frac { \partial f }{ \partial x } (0,0),\frac { \partial f }{ \partial y } (0,0).\)

  10. Let w(x, y) = xy+\(\frac { { e }^{ y } }{ { y }^{ 2 }+1 } \) for all (x, y) ∈ R2. Calculate \(\frac { { \partial }^{ 2 }w }{ { \partial y\partial x } } \) and \(\frac { { \partial }^{ 2 }w }{ { \partial x\partial y } } \)

  11. Let (x, y) = e-2y cos(2x) for all (x, y) ∈ R2. Prove that u is a harmonic function in R2.

  12. Let \(f(x,y)=\frac { { y }^{ 2 }-xy }{ \sqrt { x } -\sqrt { y } } \) for (x, y) ≠ (0, 0). Show that \(\begin{matrix} lim \\ (x,y)\rightarrow (0,0) \end{matrix}\) f(x, y) = 0

  13. Evaluate \(\begin{matrix} lim \\ (x,y)\rightarrow (0,0) \end{matrix}cos=\left( \frac { { e }^{ x }siny }{ y } \right) \), if the limit exists.

  14. Let g(x, y) = \(\frac { { x }^{ 2 }y }{ { x }^{ 4 }+{ y }^{ 2 } } \) for (x, y) ≠ (0, 0) and f(0, 0) = 0
    Show that \(\begin{matrix} lim \\ (x,y)\rightarrow (0,0) \end{matrix}\) g(x, y) = 0 along every line y = mx, m ∈ R

  15. Let g(x, y) = \(\frac { { x }^{ 2 }y }{ { x }^{ 4 }+{ y }^{ 2 } } \) for (x, y) ≠ (0, 0) and f(0, 0) = 0
    Show that \(\begin{matrix} lim \\ (x,y)\rightarrow (0,0) \end{matrix}\) g(x, y) = \(\frac { k }{ 1+{ k }^{ 2 } } \) along every parabola y = kx2, k ∈ R \ {0}.

  16. Find the partial derivatives of the following functions at the indicated point.
    f(x, y) = 3x2 - 2xy + y2 + 5x + 2, (2,-5)

  17. Find the partial derivatives of the following functions at the indicated point
    g(x, y) = 3x2 + y2 + 5x + 2, (1, -2)

  18. Find the partial derivatives of the following functions at the indicated point
    h (x, y, z) = x sin (xy) + z2x, \(\left( 2,\frac { \pi }{ 4 }, 1\right) \) 

  19. Find the partial derivatives of the following functions at the indicated point
    G(x, y) = ex+3y log (x2 + y2), (-1, 1)

  20. If U(x, y, z) = log (x3 + y3 + z3), find \(\frac { \partial U }{ \partial x } +\frac { \partial U }{ \partial y } +\frac { \partial U }{ \partial z } \)

  21. If v(x, y, z) = x3 + y3 + z3 + 3xyz, show that \(\frac { { \partial }^{ 2 }v }{ \partial y\partial z } =\frac { { \partial }^{ 2 }v }{ \partial z\partial y } \)

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

  23. If v(x, y) = x2 - xy + \(\frac14\) y + 7, x, y ∈ R, find the differential dv.

  24. If u (x, y) = x2y + 3xy4, x = et and y = sin t, find \(\frac{du}{dt}\) and evaluate If at t = 0. 

  25. If u(x, y, z) = xy2z3, x = sin t, y = cos t, z = 1+ e2t, find \(\frac{du}{dt}\)

  26. If w (x, y, z) = x2 + y2 + y2, x = et, y = esin t, z = et cos t, find \(\frac{dw}{dt}\)

  27. If w(x, y) = 6x2 - 3xy + 2y2, x = ex, y = cos s, s ∈ R find \(\frac{dw}{ds}\), and evaluate at s = 0

  28. In each of the following cases, determine whether the following function is homogeneous or not. If it is so, find the degree.
    f(x, y) = x2y + 6x3 + 7

  29. Determine whether the following function is homogeneous or not. If it is so, find the degree.
    \(h(x,y)=\frac { 6{ x }^{ 2 }{ y }^{ 3 }-\pi { y }^{ 5 }+9{ x }^{ 4 }y }{ 2020{ x }^{ 2 }+2019{ y }^{ 2 } } \)

  30. In each of the following cases, determine whether the following function is homogeneous or not. If it is so, find the degree.
    \(g(x,y,z)=\frac { \sqrt { { 3 }x^{ 2 }+5{ y }^{ 2 }+{ z }^{ 2 } } }{ 4x+7y } \)

  31. In each of the following cases, determine whether the following function is homogeneous or not. If it is so, find the degree.
    \(U(x,y,z)=xy+sin\left( \frac { { y }^{ 2 }-2{ x }^{ 2 } }{ xy } \right) \)

  32. If u(x, y) = \(\frac { { x }^{ 2 }+{ y }^{ 2 } }{ \sqrt { x+y } } \), prove that \(x\frac { \partial u }{ \partial x } +y\frac { \partial u }{ \partial y } =\frac { 3 }{ 2 } u\)

  33. Show that F(x,y) = \(\frac { { x }^{ 2 }+5xy-10{ y }^{ 2 } }{ 3x+7y } \) is a homogeneous function of degree 1.

  34. Let f (x, y) = 0 if xy ≠ 0 and f (x, y) =1 if xy = 0.
    Show that f is not continuous at (0,0)

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