1. ## vector fields

I don't understand how to solve problems that look like this;

Evaluate the integral f dr for the vector field F= yi -xj counterclockwise along the unit circle x^2 + y^2=1 from (1,0) to (0,1)

Does anyone know how to go about solving something like this...

2. Originally Posted by s7b
I don't understand how to solve problems that look like this;

Evaluate the integral f dr for the vector field F= yi -xj counterclockwise along the unit circle x^2 + y^2=1 from (1,0) to (0,1)

Does anyone know how to go about solving something like this...
$x=\cos t, \ y=\sin t, \ \ 0 \leq t \leq \frac{\pi}{2}.$ so $\int F \cdot dr = \int ydx - x dy = -\int_0^{\frac{\pi}{2}} \ dt=\frac{-\pi}{2}.$