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Vector Algebra

Question
CBSEENMA12032809

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 4

Solution

A.

straight pi

The equation of circle is
                  straight x squared plus straight y squared space equals space 4                   ...(1)
We are to find the area of the circle lying between the lines x = 0 and x = 2 in the first quadrant. 
Required area = integral subscript 0 superscript 2 straight y space dx
                       equals space integral subscript 0 superscript 2 square root of 4 minus straight x squared space end root dx                               open square brackets because space space space of space left parenthesis 1 right parenthesis close square brackets

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

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