Prove that the curves y2 = 4x and x2 = 4y divide the area of t

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 Multiple Choice QuestionsMultiple Choice Questions

81.

Area lying between the curves y2 = 4x and y = 2x  is

  • 2 over 3
  • 1 third
  • 1 fourth
  • 1 fourth
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82. Area bounded by the curve y = x3  the x-axis and the ordinates x - 2 and a = 1 is
  • -9

  • fraction numerator negative 15 over denominator 4 end fraction
  • 15 over 4
  • 15 over 4
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83. The area bounded by the curve y = x |x|, x-axis and the ordinates x = - 1 and x = 1 is given by
  • 0

  • 1 third
  • 2 over 3
  • 2 over 3
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84. The area of the circle x +y =16 exterior to the parabola y2 = 6x is
  • 4 over 3 left parenthesis 4 straight pi minus square root of 3 right parenthesis
  • 4 over 3 left parenthesis 4 straight pi plus square root of 3 right parenthesis
  • 4 over 3 left parenthesis 8 straight pi minus square root of 3 right parenthesis
  • 4 over 3 left parenthesis 8 straight pi minus square root of 3 right parenthesis
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85.

The area bounded by the x-axis, y = cosx and y = sin x when 0 less or equal than straight x less or equal than straight pi over 2

  • 2 left parenthesis square root of 2 minus 1 right parenthesis
  • square root of 2 minus 1
  • square root of 2 plus 1
  • square root of 2 plus 1
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 Multiple Choice QuestionsLong Answer Type

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86. Prove that the curves y2 = 4x and x2 = 4y divide the area of the square bounded by x = 0, x = 4, y = 4 and y = 0 into three equal parts.


The equation of curves are
                              straight y squared space equals space 4 straight x                   ...(1)
                  and      straight x squared space equals space 4 straight y                  ...(2)
From (2),  straight y equals straight x squared over 4                                 ...(3)
Putting this value of y in (1),
straight x to the power of 4 over 16 space equals space 4 straight x space space space or space space straight x to the power of 4 space equals space 64 straight x
or   straight x left parenthesis straight x cubed minus 64 right parenthesis space equals space 0
therefore space space space space straight x space equals space 0 comma space 4
therefore space space space from space left parenthesis 3 right parenthesis comma space space straight y space equals space 0 comma space space 4
because space space space curves space left parenthesis 1 right parenthesis space and space left parenthesis 2 right parenthesis space intersect space in space straight O left parenthesis 0 comma space 0 right parenthesis comma space straight P left parenthesis 4 comma space 4 right parenthesis

From P. draw PM ⊥ x-axis.
Required area = Area OAPB = Area OBPM - area OAPM
                        equals space integral subscript 0 superscript 4 square root of 4 straight x end root space dx space minus space integral subscript 0 superscript 4 straight x squared over 4 dx space equals space 2 integral subscript 0 superscript 4 straight x to the power of 1 half end exponent dx minus 1 fourth integral subscript 0 superscript 4 straight x squared dx space equals space 2 open square brackets fraction numerator straight x to the power of begin display style 3 over 2 end style end exponent over denominator begin display style 3 over 2 end style end fraction close square brackets subscript 0 superscript 4 minus 1 fourth open square brackets straight x cubed over 3 close square brackets subscript 0 superscript 4
equals space 2 space cross times space 2 over 3 open square brackets straight x to the power of 3 over 2 end exponent close square brackets subscript 0 superscript 4 space minus 1 fourth cross times 1 third open square brackets straight x cubed close square brackets subscript 0 superscript 4 space equals space 4 over 3 open square brackets open parentheses 4 close parentheses to the power of 3 over 2 end exponent minus 0 close square brackets space minus space 1 over 12 open square brackets left parenthesis 4 right parenthesis cubed minus 0 close square brackets
equals space 4 over 3 cross times 8 minus 1 over 12 cross times 64 space equals space 32 over 3 minus 16 over 3 equals space 16 over 3 space sq. space units.
Now, the area of the region OAQBO bounded by curves straight y squared space equals 4 straight x and straight x squared space equals space 4 straight y


                                 equals space integral subscript 0 superscript 4 open parentheses 2 square root of straight x minus straight x squared over 4 close parentheses dx
equals space open square brackets 2 cross times 2 over 3 straight x to the power of 3 over 2 end exponent minus straight x cubed over 12 close square brackets subscript 0 superscript 4
equals space open square brackets 4 over 3 cross times 4 to the power of 3 over 2 end exponent minus fraction numerator left parenthesis 4 right parenthesis cubed over denominator 12 end fraction close square brackets space minus space left parenthesis 0 minus 0 right parenthesis
equals space 4 over 3 cross times 8 minus 16 over 3 equals 32 over 3 minus 16 over 3 equals 16 over 3 space space space space space space space space space space space space space space space space space space space space space space space space... left parenthesis 1 right parenthesis

Again, the area of the region OPQAO bounded by the curves x2 = 4 y, x = 0, x = 4 and x-axis
equals space integral subscript 0 superscript 4 straight x squared over 4 dx space equals space space 1 over 12 open square brackets straight x cubed close square brackets subscript 0 superscript 4
equals space 1 over 12 left parenthesis 4 cubed minus 0 right parenthesis space equals space 1 over 12 cross times 64 space equals space 16 over 3 space space space space space space space space space space space space space space... left parenthesis 2 right parenthesis
Similarly, the area of the region OBQRO bounded by the curve straight y squared space equals space 4 straight x comma space space straight y space equals space 0 space space and space space straight y space equals 4
equals space integral subscript 0 superscript 4 space straight x space dy space equals space integral subscript 0 superscript 4 straight y squared over 4 dy space equals space 1 over 12 open square brackets straight y cubed close square brackets subscript 0 superscript 4 space equals space 16 over 3    ...(3)
From (1), (2) and (3), it is clear that the area of the region OAQBO = area of the region OPQAO = area of the region OBQRO, i.e., urea bounded by parabolas y2 = 4 x and x2 = 4 y divides the area of the square in three equal parts.

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87.

Using the method of integration, find the area of the triangular region whose vertices are (2, -2), (4, 3) and (1, 2).

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88.

Sketch the region bounded by the curves straight y equals square root of 5 minus straight x squared end root space and space straight y space equals open vertical bar straight x minus 1 close vertical bar and find its area using integration. 

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89.

Using integration, find the area of the region bounded by the triangle whose vertices are (-1, 2), (1, 5) and (3, 4).

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90.

Using integration, find the area bounded by the curve x2 = 4y and the line x = 4y – 2.

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