-->

Vector Algebra

Question
CBSEENMA12032749

Find the area of the region enclosed between the two circles x2 + y2 = 4 and (x - 2)2 + y2 = 4.

Solution
The equations of the given circles are
                           straight x squared plus straight y squared space equals space 4 space space space space space space... left parenthesis 1 right parenthesis
and                left parenthesis straight x minus 2 right parenthesis squared plus straight y squared space equals space 4  ...(2)
  Equation (1) is a circle with centre O at the origin and radius 2. Equation (2) is a circle with centre C(2, 0) and radius 2.
    Solving equations (1) and (2), we have
                        left parenthesis straight x minus 2 right parenthesis squared plus straight y squared space equals space straight x squared plus straight y squared
or                 straight x squared minus 4 straight x plus 4 plus straight y squared space equals space straight x squared plus straight y squared
or                  negative 4 straight x plus 4 space equals space 0 space space space space space space space rightwards double arrow space space space straight x space minus space 1 space equals 0
or                       x = 1
therefore   from  (1),      1 plus straight y squared space equals space 4 space space space space or space space straight y squared space equals space 3
therefore space space space space space space straight y space equals space plus-or-minus square root of 3


therefore the points of intersection of the given circles are straight A left parenthesis 1 comma space square root of 3 right parenthesis space and space straight A left parenthesis 1 comma space minus square root of 3 right parenthesis end root.
Required area of the enclosed region OACA'O between the circles
      = 2 [area of region ODCAO]
      =2 [area of region ODAO + area of the region DCAD]
      equals space 2 open square brackets integral subscript 0 superscript 1 straight y space dx space plus space integral subscript 1 superscript 2 straight y space dx close square brackets space equals space 2 open square brackets integral subscript 0 superscript 1 square root of 4 minus left parenthesis straight x minus 2 right parenthesis squared end root space dx space plus integral subscript 1 superscript 2 square root of 4 minus straight x squared end root dx close square brackets
equals space 2 open square brackets 1 half left parenthesis straight x minus 2 right parenthesis space square root of 4 minus left parenthesis straight x minus 2 right parenthesis squared end root plus 1 half cross times 4 space sin to the power of negative 1 end exponent open parentheses fraction numerator straight x minus 2 over denominator 2 end fraction close parentheses close square brackets subscript 0 superscript 1
                                                                           plus 2 space open square brackets 1 half straight x square root of 4 minus straight x squared end root plus 1 half cross times 4 space sin to the power of negative 1 end exponent straight x over 2 close square brackets subscript 1 superscript 2
        equals space open square brackets left parenthesis straight x minus 2 right parenthesis space square root of 4 minus left parenthesis straight x minus 2 right parenthesis squared end root plus 4 space sin to the power of negative 1 end exponent open parentheses fraction numerator straight x minus 2 over denominator 2 end fraction close parentheses close square brackets subscript 0 superscript 1 plus open square brackets straight x square root of 4 minus straight x squared end root plus 4 space sin to the power of negative 1 end exponent straight x over 2 close square brackets subscript 1 superscript 2
equals space open square brackets open parentheses negative square root of 3 plus 4 space sin to the power of negative 1 end exponent open parentheses fraction numerator negative 1 over denominator 2 end fraction close parentheses close parentheses minus 4 space sin to the power of negative 1 end exponent left parenthesis negative 1 right parenthesis close square brackets plus open square brackets 4 space sin to the power of negative 1 end exponent 1 space minus square root of 3 minus 4 space sin to the power of negative 1 end exponent 1 half close square brackets
equals space open square brackets open parentheses negative square root of 3 minus 4 cross times straight pi over 6 close parentheses plus 4 cross times straight pi over 2 close square brackets plus open square brackets 4 cross times straight pi over 2 minus square root of 3 minus 4 cross times straight pi over 6 close square brackets
equals space open parentheses negative square root of 3 minus fraction numerator 2 straight pi over denominator 3 end fraction plus 2 straight pi close parentheses plus open parentheses 2 space straight pi space minus square root of 3 minus fraction numerator 2 straight pi over denominator 3 end fraction close parentheses space equals space fraction numerator 8 straight pi over denominator 3 end fraction minus 2 square root of 3

Some More Questions From Vector Algebra Chapter