Use Green's Theorem to evaluate C F · dr. (Check the orientation of the curve before applying the theorem.) F(x, y) = e2x + x2y, e2y − xy2 C is the circle x2 + y2 = 9 oriented clockwise

Respuesta :

Answer:

Using Green's theorem we get,

[tex]I= \frac{-81\pi}{2}[/tex]

Step-by-step explanation:

Given function is F(x,y)=[tex](e^{2x} +x^{2}y,e^{2y} -y^{2}x)[/tex]

and path C is circle : [tex]x^{2} +y^{2} =9[/tex] clockwise.

Theory : Green's theorem is given by

[tex]I= \int\int\limits_C (\frac{\delta Q}{\delta x} -\frac{\delta P}{\delta y}) \, dx dy[/tex]

Where C is region bounded by curve in counterclockwise.

and F(x,y) = (P,Q)

Using Green's theorem,

F(x,y)=[tex](e^{2x} +x^{2}y,e^{2y} +y^{2}x)[/tex] and F(x,y) = (P,Q)

P=[tex]e^{2x} +x^{2}y[/tex]

Q=[tex]e^{2y} -y^{2}x[/tex]

Now,

[tex]\frac{\delta P}{\delta y}=\frac{\delta }{\delta y}(e^{2x} +x^{2}y)[/tex]

[tex]\frac{\delta P}{\delta y}=\frac{\delta }{\delta y}e^{2x} +\frac{\delta }{\delta y}x^{2}y[/tex]

[tex]\frac{\delta P}{\delta y}=0+x^{2}[/tex]

Also,

[tex]\frac{\delta Q}{\delta x}=\frac{\delta }{\delta x}(e^{2y} -y^{2}x)[/tex]

[tex]\frac{\delta Q}{\delta x}=\frac{\delta }{\delta x}e^{2y} -\frac{\delta }{\delta x}y^{2}x[/tex]

[tex]\frac{\delta Q}{\delta x}=-y^{2}[/tex]

Replacing the value in Green's theorem,

[tex]I= \int\int\limits_C (\frac{\delta Q}{\delta x} -\frac{\delta P}{\delta y})  \, dx dy[/tex]

[tex]I= \int\int\limits_C ( y^{2}+x^{2})  \, dx dy[/tex]

Introducing polar coordinates.

Take x=rcosu

        y=rsinu

        dxdy=rdrdu

Limits : r=0 to r=3

         : u=0 to u={tex}2\pi{/tex}

[tex]I= \int\limits^{2\pi}_0\int\limits^3_0 ((rsinu)^{2}+(rcosu)^{2})  \, rdrdu\\I= \int\limits^{2\pi}_0\int\limits^3_0 [(r^{2}sin^{2}u)+(r^{2}cos^{2}u)] \, rdrdu\\I= \int\limits^{2\pi}_0\int\limits^3_0 [r^{2}] \, rdrdu\\I= \int\limits^{2\pi}_0\int\limits^3_0[r^{3}] \, drdu\\I= \int\limits^{2\pi}_0[\frac{r^{4}}{4}]^3_0 \, drdu\\I= \int\limits^{2\pi}_0[\frac{3^{4}}{4}] \, drdu\\I=\frac{3^{4}}{4}(2\pi-0)\\\\I= \frac{81}{4}(2\pi)[/tex]

Given curve C is clockwise.

Therefore,

[tex]I= (-1)\frac{81}{4}(2\pi)[/tex]

[tex]I= \frac{-81}{4}(2\pi)[/tex]

[tex]I= \frac{-81\pi}{2}[/tex]