Skip to main content ?

Section 16.7 : Green's Theorem

  1. Use Green’s Theorem to evaluate \( \displaystyle \int\limits_{C}{{y{x^2}\,dx - {x^2}\,dy}}\) where \(C\) is shown below.
    The curve \(C\).  It is a closed curve made up of the left half of the circle \({x^2} + {y^2} = 25\) together with the portion of the y-axis from \(\left( {0, - 5} \right)\) to \(\left( {0,5} \right)\).  The arrows show that the curve starts at \(\left( {0,5} \right)\), travels around the semicircle through \(\left( { - 5,0} \right)\) to \(\left( {0, - 5} \right)\) and then back up the y-axis to the starting point.
    Solution
  2. Use Green’s Theorem to evaluate \( \displaystyle \int\limits_{C}{{\left( {6y - 9x} \right)dy - \left( {yx - {x^3}} \right)\,dx}}\) where \(C\) is shown below.
    The curve \(C\).  It is a closed four sided figure with corners at \(\left( { - 1,4} \right)\), \(\left( { - 1, - 1} \right)\), \(\left( {1, - 1} \right)\) and \(\left( {1,2} \right)\).  The arrows show that it is traveled in the counter clockwise direction, going down the left side, right along the bottom, up the right side and then back up along the slanted top side to \(\left( { - 1,4} \right)\).
    Solution
  3. Use Green’s Theorem to evaluate \( \displaystyle \int\limits_{C}{{{x^2}{y^2}\,dx + \left( {y{x^3} + {y^2}} \right)\,dy}}\) where \(C\) is shown below.
    The curve \(C\).  It is a closed triangle with corners at the origin, \(\left( {4,2} \right)\) and \(\left( {4, - 8} \right)\).  The arrows show that it is traveled in the clockwise direction, going from the origin up to \(\left( {4,2} \right)\), straight down the right side to \(\left( {4, - 8} \right)\) and then back up to the origin.
    Solution
  4. Use Green’s Theorem to evaluate \( \displaystyle \int\limits_{C}{{\left( {{y^4} - 2y} \right)\,dx - \left( {6x - 4x{y^3}} \right)\,dy}}\) where \(C\) is shown below.
    The curve \(C\).  It is the closed rectangle with corners at the origin, \(\left( {6,0} \right)\), \(\left( {6,4} \right)\) and \(\left( {0,4} \right)\).  The arrows show that it is traveled in the counter clockwise direction, going right along the bottom, up the right side, left across the top and back down the left side.
    Solution
  5. Verify Green’s Theorem for \( \displaystyle \oint_{C}{{\left( {x{y^2} + {x^2}} \right)\,dx + \left( {4x - 1} \right)\,dy}}\) where \(C\) is shown below by (a)computing the line integral directly and (b) using Green’s Theorem to compute the line integral.
    The curve \(C\).  It is the closed triangle with corners at \(\left( { - 3,0} \right)\), the origin and \(\left( {0,3} \right)\).  The arrows show that it is traveled in the counter clockwise direction, going right along the x-axis to the origin, up the y-axis to \(\left( {0,3} \right)\) and then back down the slanted side to \(\left( { - 3,0} \right)\).
    Solution