Line integral across a vector field

clandarkfire
Messages
31
Reaction score
0

Homework Statement


\int_C \mathbf F\cdot d \mathbf r where \mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}
and C is the segment of y=x^2 from (-1,1) to (1,1).

Homework Equations


\int_C \mathbf F\cdot d \mathbf r=\int_a^b \mathbf F( \mathbf r(t))\cdot r'(t) dt=\int_C Pdx+Qdy where \mathbf F = P\vec{i}+Q\vec{j}

The Attempt at a Solution


I parametrize C:
\mathbf r(t)=<t,t^2>|-1\leq t \leq 1
Well, I know how to apply the equations above as well as Green's theorem (I use this by letting C2 be a line from (1,1) to (-1,1) and integrating across the enclosed disk D), but no matter what I do, I find myself having to integrate some version of e^{\sin^4{y}}
There has to be some trick I'm missing. Could someone point me in the right direction?
 
Physics news on Phys.org
clandarkfire said:

Homework Statement


\int_C \mathbf F\cdot d \mathbf r where \mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}
and C is the segment of y=x^2 from (-1,1) to (1,1).

Homework Equations


\int_C \mathbf F\cdot d \mathbf r=\int_a^b \mathbf F( \mathbf r(t))\cdot r'(t) dt=\int_C Pdx+Qdy where \mathbf F = P\vec{i}+Q\vec{j}

The Attempt at a Solution


I parametrize C:
\mathbf r(t)=<t,t^2>|-1\leq t \leq 1
Well, I know how to apply the equations above as well as Green's theorem (I use this by letting C2 be a line from (1,1) to (-1,1) and integrating across the enclosed disk D), but no matter what I do, I find myself having to integrate some version of e^{\sin^4{y}}
There has to be some trick I'm missing. Could someone point me in the right direction?
If \displaystyle \mathbf r(t)=<t,\,t^2>\,,\ then \displaystyle d\mathbf r(t)=<1,\,2t>dt\ .

You will have an odd integrand involving the problematic \displaystyle e^{\sin^4{y}}\ .
 
Last edited:
Does this get me anywhere? It seems to still leave me with something unsolveable.
 
Check for independence of path and use the straight line from (-1,1) to (1,1).
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top