00:01
For this problem, we are asked to compute the line integral of the vector field f of xy equals the vector negative to y.
00:07
For the half circle, x squared plus y squared equals 1 with y greater than or equal to zero, oriented counterclockwise.
00:17
So our first step here is to parameterize our curve, r of t.
00:22
Now, the standard parameterization for a circle would be r -coast -t, r -sign -t.
00:28
We clearly have a radius of 1.
00:30
So we'd have coast t, sine t, and note that we are oriented counterclockwise.
00:40
So we would be going in the standard direction of increasing t or increasing theta here.
00:46
But we do need to keep in mind that we are restricted to why greater than are equal to zero.
00:51
So this isn't going to be for t between 0 and 2 pi, but rather for t between 0 and pi.
00:59
Using that then, we'd have that r prime of t is going to equal negative sine of t.
01:09
Oops, that was a sloppy t there.
01:11
Negative sign of t, cose of t, which then means that the magnitude of r prime is going to equal...