Evaluate ,  where x is a fixed positive number, Hence, prove t

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 Multiple Choice QuestionsLong Answer Type

71. Draw a rough sketch of the region {(x, y): y2 ≤ 3 x, 3 x2 + 3 y2 ≤ 16} and find the area enclosed by the region using method of integration.
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72.

Find the area of the smaller part of the circle x2 + y2 = a cut oil by the line straight x equals fraction numerator straight a over denominator square root of 2 end fraction

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73. Find the area of the smaller region bounded by the ellipse straight x squared over 9 plus straight y squared over 4 space equals space 1 and the straight line straight x over 3 plus straight y over 2 space equals space 1.
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74.

Using integration, find the area of the smaller region bounded by the curve straight x squared over 16 plus straight y squared over 9 space equals space 1 and the straight line straight x over 4 plus straight y over 3 equals 1.

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75.

Find the area of smaller region bounded by the ellipse straight x squared over straight a squared plus straight y squared over straight b squared space equals 1 and the straight line straight x over straight a plus straight y over straight b equals 1

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76. Evaluate integral subscript 0 superscript straight r square root of straight r squared minus straight x squared end root dx,  where x is a fixed positive number, Hence, prove that the area of a circle of radius r is straight pi space straight r squared.


Let I = integral subscript 0 superscript straight r square root of straight r squared minus straight x squared end root space dx
          equals space open square brackets fraction numerator straight x square root of straight r squared minus straight x squared end root over denominator 2 end fraction plus straight r squared over 2. sin to the power of negative 1 end exponent open parentheses straight x over straight r close parentheses close square brackets subscript 0 superscript straight r
equals space open square brackets fraction numerator straight r square root of straight r squared minus straight r squared end root over denominator 2 end fraction plus straight r squared over 2 sin to the power of negative 1 end exponent open parentheses straight r over straight r close parentheses close square brackets space minus space open square brackets 0 plus straight r squared over 2 sin to the power of negative 1 end exponent left parenthesis 0 right parenthesis close square brackets
space equals space open square brackets 0 plus straight r squared over 2 sin to the power of negative 1 end exponent left parenthesis 1 right parenthesis close square brackets space minus space open square brackets 0 plus straight r squared over 2 sin to the power of negative 1 end exponent left parenthesis 0 right parenthesis close square brackets space equals space 0 plus straight r squared over 2 cross times straight pi over 2 minus 0 space equals space πr squared over 4


Let straight f left parenthesis straight x right parenthesis space equals space straight y space equals space square root of straight r squared minus straight x squared end root

Now straight y equals space square root of straight r squared minus straight x squared end root   rightwards double arrow space space space straight y squared space equals space straight r squared minus straight x squared
rightwards double arrow space space space space space straight x squared plus straight y squared space equals space straight r squared comma space space which space is space straight a space circle space at space the space origin space and space radius space straight r.
therefore space space space space integral subscript 0 superscript straight r square root of straight r squared minus straight x squared end root space space dx  represents the area bounded  by the circle straight x squared plus straight y squared space equals space straight r squared comma the x-axis and the ordinate x = 0 and the ordinate x = r, i.e., it represents the area of the region in the first quadrant. 
therefore space space space space area space of space circle space equals space 4. space open parentheses πr squared over 4 close parentheses space equals space straight pi space straight r squared.

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 Multiple Choice QuestionsShort Answer Type

77.

Find the whole area of the circle x2 + y2 = a2.

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 Multiple Choice QuestionsMultiple Choice Questions

78. Area lying in the first quadrant and bounded by the circle x2 + y2 = 4 and the lines x = 0 and x = 2 is
  • straight pi
  • straight pi over 2
  • straight pi over 3
  • straight pi over 3
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79. Area of the region bounded by the curve y2 = 4 x, y-axis and the line y = 3 is
  • 2

  • 9 over 4
  • 9 over 3
  • 9 over 3
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80. Smaller area enclosed by the circle x2 + y2 = 4 and the line x + y = 2 is
Choose the correct answer.
or
Draw the rough sketch and find the area of the region:
{(x, y): x2 + y2 < 4, x + y > 2}.  

  • 2 space left parenthesis straight pi space minus space 2 right parenthesis
  • straight pi space minus 2
  • 2 straight pi minus 1
  • 2 straight pi minus 1
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