Find the area of the region enclosed by the parametric equation
x=t^3–7t
y=8t^2
x=t^3–7t
y=8t^2
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This is best done by plotting the curve:
Link:
http://www.wolframalpha.com/input/?i=par…
The entry and exit of the loop occurs when x = 0.
t^3 - 7t = 0
==> t = 0, ±√7.
(We ignore t = 0, since that yields (0, 0) which is certainly not where the curve crosses itself.)
Hence, the area ∫ y dx equals
∫(t = -√7 to √7) (8t^2) * (3t^2 - 7) dt
= 2 ∫(t = 0 to √7) (8t^2) * (3t^2 - 7) dt, since the integrand is even
= 2 ∫(t = 0 to √7) (24t^4 - 56t^2) dt
= 2(24t^5/5 - 56t^3/3) {for t = 0 to √7}
= (3136/15)√7.
I hope this helps!
Link:
http://www.wolframalpha.com/input/?i=par…
The entry and exit of the loop occurs when x = 0.
t^3 - 7t = 0
==> t = 0, ±√7.
(We ignore t = 0, since that yields (0, 0) which is certainly not where the curve crosses itself.)
Hence, the area ∫ y dx equals
∫(t = -√7 to √7) (8t^2) * (3t^2 - 7) dt
= 2 ∫(t = 0 to √7) (8t^2) * (3t^2 - 7) dt, since the integrand is even
= 2 ∫(t = 0 to √7) (24t^4 - 56t^2) dt
= 2(24t^5/5 - 56t^3/3) {for t = 0 to √7}
= (3136/15)√7.
I hope this helps!
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ok so draw the goddamn thing on X axis and Y axis and see what the enclosed area is......read your book.