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

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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.
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 Multiple Choice QuestionsShort Answer Type

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77.

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


The equation of circle is x2 + y2 = a2     ...(1)
Its centre is origin and radius a. We know that circle x2 + y2 = a2 is symmetrical about both axes.
therefore space space space required space area space equals space 4 space integral subscript 0 superscript straight a straight y space dx space equals space 4 space integral subscript 0 superscript straight a square root of straight a squared minus straight x squared end root space dx

                  equals space 4 open square brackets fraction numerator straight x square root of straight a squared minus straight x squared end root over denominator 2 end fraction plus straight a squared over 2 sin to the power of negative 1 end exponent straight x over straight a close square brackets subscript 0 superscript straight a
equals space 4 open square brackets open parentheses 0 plus straight a squared over 2 sin to the power of negative 1 end exponent 1 close parentheses space minus space open parentheses 0 plus straight a squared over 2 sin to the power of negative 1 end exponent 0 close parentheses close square brackets
equals space 4 open square brackets open parentheses 0 plus straight a squared over 2 sin to the power of negative 1 end exponent 1 close parentheses space minus space open parentheses 0 plus straight a squared over 2 sin to the power of negative 1 end exponent 0 close parentheses close square brackets
equals 4 space open square brackets straight a squared over 2 cross times straight pi over 2 close square brackets space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space open square brackets because space sin to the power of negative 1 end exponent 0 space equals space 0 close square brackets
space equals space straight pi space straight a space.



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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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