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Line integral.....Help!

I have tried this simple question 3 or 4 times (revisiting) , and i know there`s something simple i`m missing:

Evaluate:

∫C(2x3y)dx+(3x+y)dy\displaystyle \int_{C} (2x^{3}y)dx+(3x+y)dy

on C: x=y3x=y^{3} from (−1,1)(-1,1) to (−1,1)(-1,1)

however i do it, i get zero!

the last time, i treated y as parameter, x=2 so dx=0 and from -1 to 1

the time before that x as parameter from 1 to 0

the answer is 26/9,

i don`t know where i`m missing something?

Please a nudge in the direction would be great!

EDITED
(edited 9 years ago)
Reply 1
Avatar for davros
davros
16
Original post by Hasufel
I have tried this simple question 3 or 4 times (revisiting) , and i know there`s something simple i`m missing:

Evaluate:

∫C(2x3y)dx+(3x+y)dy\displaystyle \int_{C} (2x^{3}y)dx+(3x+y)dy

on C: y=x3y=x^{3} from (−1,1)(-1,1) to (−1,1)(-1,1)

however i do it, i get zero!

the last time, i treated y as parameter, x=2 so dx=0 and from -1 to 1

the time before that x as parameter from 1 to 0

the answer is 26/9,

i don`t know where i`m missing something?

Please a nudge in the direction would be great!


I'm confused!

(-1, 1) doesn't lie on the curve C: y = x^3.

Also you seem to be starting and ending at the same point - is this what you intended?

And where does x = 2 come from??


Can you give us a screenshot of the exact question or re-check the wording please?
Hasufel
..
I have no idea what your curve is supposed to be. The start and end points are identical and neither of them actually lie on the curve y=x^3.
Reply 3
Avatar for davros
davros
16
Original post by DFranklin
I have no idea what your curve is supposed to be. The start and end points are identical and neither of them actually lie on the curve y=x^3.


:biggrin:
Reply 4
Avatar for Hasufel
Hasufel
OP
16
Original post by davros
I'm confused!

(-1, 1) doesn't lie on the curve C: y = x^3.

Also you seem to be starting and ending at the same point - is this what you intended?

And where does x = 2 come from??


Can you give us a screenshot of the exact question or re-check the wording please?



Original post by DFranklin
I have no idea what your curve is supposed to be. The start and end points are identical and neither of them actually lie on the curve y=x^3.


C**p! my apologies to you both!

the curve is actually x=y3x=y^{3}

SORRY!
(edited 9 years ago)
Original post by Hasufel
C**p! my apologies to you both!

the curve is actually x=y3x=y^{3}And still ... The start and end points are identical and neither of them actually lie on the curve x = y^3
Reply 6
Avatar for Hasufel
Hasufel
OP
16
Original post by DFranklin
And still ... The start and end points are identical and neither of them actually lie on the curve x = y^3


Sorry!

i`ll start again:

Evaluate:

∫C(2x3y)dx+(3x+y)dy\displaystyle \int_{C} (2x^{3}y)dx+(3x+y)dy

on C: x=y3x=y^{3} from (1,−1)(1,-1) to (1,1)(1,1)

that`s what the Q says - have they the limits wrong?
(edited 9 years ago)
Original post by Hasufel
Sorry!

i`ll start again:

Evaluate:

∫C(2x3y)dx+(3x+y)dy\displaystyle \int_{C} (2x^{3}y)dx+(3x+y)dy

on C: x=y3x=y^{3} from (1,−1)(1,-1) to (1,1)(1,1)

that`s what the Q says
This still makes no sense. (1, -1) does not lie on the curve x = y^3.
Reply 8
Avatar for Hasufel
Hasufel
OP
16
Original post by DFranklin
This still makes no sense. (1, -1) does not lie on the curve x = y^3.


Thanks - i think that the limits are wrong, and i have misinterpreted the Q anyway!
(edited 9 years ago)

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