Integrate from the centroid of a semi circle?

GROUPS:
 I am confused by this prospect. We have a semicircle with radius r whose centroid is given by 4r/3pi. Can we obtain the area of the semi circle by integrating from the centroid of the semi circle.I saw that we could integrate from the centre of the full circle by evaluating integral through a sector like this But how could we do it from the centroid of the semi circle?