Calculate the curve integral ∮ (x ^ 2 + y ^ 2) ds C as x = acost, y = asint (0

This problem can be skillfully done x ^ 2 + y ^ 2 = a ^ 2, a is a constant, and from the equation, we can see that C is a circle, so ∮ DS = 2 π a, so ∮ (x ^ 2 + y ^ 2) ds = ∮ a ^ 2ds = a ^ 2 & nbsp; ∮ DS = a ^ 2 & nbsp; * & nbsp; 2 π a = 2 π a ^ 3. The general practice is shown in the figure

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