Q. Use Green's theorem to evaluate the line integral along the given positively oriented curve.∫C7y3dx−7x3dy,C is the circle x2+y2=4
Rephrase the problem: Step 1: Rephrase the problem.question_prompt: Use Green's theorem to evaluate the line integral along the given positively oriented curve for the function 7y3dx−7x3dy, where C is the circle x2+y2=4.
Apply Green's theorem: Step 2: Apply Green's theorem.Green's theorem relates a line integral around a simple, closed, positively oriented curve C to a double integral over the plane region D bounded by C. Green's theorem states:∫CPdx+Qdy=∫∫D(∂x∂Q−∂y∂P)dA,where P=7y3 and Q=−7x3.
Set up the double integral: Step 4: Set up the double integral. ∫∫D(−21x2−21y2)dA.
Convert to polar coordinates: Step 5: Convert to polar coordinates.Since D is a circle of radius 2, convert the integral to polar coordinates where x=rcos(θ) and y=rsin(θ). Then, x2+y2=r2 and dA=rdrdθ.∫∫D(−21r2)rdrdθ=−21∫02π∫02r3drdθ.
Evaluate the integral: Step 6: Evaluate the integral.−21∫02π[r4/4]02dθ=−21∫02π(16/4)dθ=−21∫02π4dθ=−21[4θ]02π=−21×8π=−168π.
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