The integral is  and  is the right half of the circle.

Definition of the line integral :

If F is a continuous vector field on a smooth curve C, the function  in the interval .

Then the line integral of F on C is .

The unit circle can be parameterized of the equation are  and .

Since the right half of the circle, integrate the function in the interval .

Then .

The line integral of  is

Consider .

Then the limits of integration will change from  to 

Substitute  and  in the above integral.

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