Solving Line Integral on Curve C

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The discussion revolves around evaluating the line integral ∫(y² - x²)ds along the curve defined by x = 3t(1+t) and y = t³ for 0 ≤ t ≤ 2. The participant calculates ds using the derivatives of x and y, resulting in ds = 3√(t⁴ + 4t² + 4t + 1)dt. They express the integral as 3∫(t⁶ - 9t² - 18t³ - 9t⁴)√(t⁴ + 4t² + 4t + 1)dt but express uncertainty about how to proceed with solving it, suggesting it seems more complex than previous classwork. The thread includes a correction of a typo, and the participant plans to return with updates if they find a solution.
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Homework Statement



Evaluate the following line integral on the indicated curve C

\int(y^2-x^2)ds

C: x = 3t(1+t), y=t^3 ; 0 <= t <= 2

Homework Equations



ds = \sqrt{(f&#039;(t))^2+(g&#039;(t))^2}dt

The Attempt at a Solution



dx/dt = 3+6t
dy/dt = 3t^2

ds = \sqrt{(3+6t)^2+(3t^2)^2}dt
ds = 3*\sqrt{t^4+4t^2+4t+1}dt

y^2 = t^6
x^2 = (3t+3t^2)^2 = 9t^2+18t^3+9t^4

\int(y^2-x^2)ds = 3\int(t^6-9t^2-18t^3-9t^4)\sqrt{t^4+4t^2+4t+1}dt

From here I don't know how to solve the integral, and it looks way more complicated than what we have done so far in class. Maybe I am doing something wrong? Or there is a trick involved here? Any help would be greatly appreciated. Thanks.
 
Last edited:
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I see a typo, but I can't offer any more help than that.
\int(y^2-x^2)ds = 3\int(t^6 -9t^2-18t^3-9t^4)\sqrt{t^4+4t^2+4t+1}dt
 
Thanks Mark44, I corrected the mistake in the first post. I will come back to this thread if I find an answer and post it.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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