Question:medium

If R is a closed region in the xy-plane bounded by a simple closed curve C and if M(x, y) and N(x, y) are continuous functions of x and y having continuous derivative in R, then

Show Hint

A simple way to remember the order of terms in Green's theorem is to think of the vector field \( \vec{F} = (M, N) \). The integrand is \( \frac{\partial(\text{second component})}{\partial(\text{first variable})} - \frac{\partial(\text{first component})}{\partial(\text{second variable})} \), which is \( \frac{\partial N}{\partial x} - \frac{\partial M}{\partial y} \). This is the 2D "curl".
Updated On: Feb 20, 2026
  • \( \oint_C Mdx + Ndy = \iint_R \left( \frac{\partial M}{\partial x} - \frac{\partial N}{\partial y} \right) dx dy \)
  • \( \oint_C Mdx + Ndy = \iint_R \left( \frac{\partial N}{\partial x} - \frac{\partial M}{\partial y} \right) dx dy \)
  • \( \oint_C Mdx + Ndy = \iint_R \left( \frac{\partial M}{\partial y} - \frac{\partial N}{\partial x} \right) dx dy \)
  • \( \oint_C Mdx + Ndy = \iint_R \left( \frac{\partial M}{\partial x} + \frac{\partial N}{\partial y} \right) dx dy \)
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Concept Identification: The objective is to present Green's theorem. This theorem establishes a connection between a line integral along a closed curve C and a double integral over the region R enclosed by C.
Step 2: Core Formula: For a vector field \( \vec{F} = M(x,y)\hat{i} + N(x,y)\hat{j} \), Green's theorem states that the line integral of \( \vec{F} \) taken counterclockwise around a simple closed curve C equals the double integral of the component of the curl of \( \vec{F} \) in the z-direction over the region R bounded by C. The line integral is expressed as \( \oint_C \vec{F} \cdot d\vec{r} = \oint_C Mdx + Ndy \). The z-component of the curl is \( (\text{curl} \vec{F})_z = \frac{\partial N}{\partial x} - \frac{\partial M}{\partial y} \). Consequently, Green's theorem is formulated as: \[ \oint_C Mdx + Ndy = \iint_R \left( \frac{\partial N}{\partial x} - \frac{\partial M}{\partial y} \right) dA \] where \( dA = dx dy \).
Step 3: Detailed Evaluation: Comparing the derived formula with the provided options:
Option (A) is incorrect due to incorrect terms and sign.
Option (B) accurately represents \( \iint_R \left( \frac{\partial N}{\partial x} - \frac{\partial M}{\partial y} \right) dx dy \), aligning with Green's theorem.
Option (C) has terms in an inverted order, leading to a sign error.
Option (D) represents the double integral of the divergence, which pertains to the flux form of Green's theorem or the 2D Divergence Theorem, not the circulation form requested.
Step 4: Conclusion: Option (B) provides the correct statement of Green's theorem.
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