True or false :
Let ϕ : [ 0 , 2 π ] → R 2 , ϕ ( t ) = ( 2 + cos t , sin t ) and let γ : [ 0 , 2 π ] → R 2 , γ ( t ) = ( cos t , sin t ) , then the equation below is satisfied.
∫ ϕ x 2 + y 2 − y d x + x 2 + y 2 x d y = ∫ γ x 2 + y 2 − y d x + x 2 + y 2 x d y
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Great! When applying a theorem, we always have to check that the initial conditions hold. It is tempting to assume that they do.
Thank you Sir..Nice solution . I will post for sure.. Thanks
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In the problem, should the second parametriation be γ ( t ) = ( cos t , sin t ) instead?
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Yes. You are right Calvin.. I made a mistake writing the problem.. I hope the members will understand this mistake of myself. I am sorry.. Cheers
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@Jose Sacramento – Thanks. I've edited the problem accordingly. Note that you, as the problem creator, can edit your own problems by selecting that option in the menu.
I recognized the integrand as the imaginary part of x + i y 1 . Since this function is analytic inside and on the closed loop ϕ , the value of the integral is zero (by the Cauchy Integral Theorem). It is not hard to show that the other integral is equal to 2 π (whether you simplify the integrand to 1 or just apply the Cauchy Integral Formula). In other words, the integrals are not equal.
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Nice problem! Please do post more problems on vector calculus.
∫ ϕ ω = 0 by Stokes' Theorem since d ω = 0 for the given 1-form ω . Note that this form is defined throughout the disc M enclosed by the circle ∂ M . (Recall that Stokes' Theorem states that ∫ ∂ M ω = ∫ M d ω )
Using the given parameterization, we see that ∫ γ ω = ∫ 0 2 π ( sin 2 t + cos 2 t ) d t = 2 π . Here we cannot use Stokes' Theorem directly since the form is undefined at the origin.
Thus the stated equation is F a l s e .