# Centroid of a Semicircle

1. Jul 20, 2009

### lizzyb

2. Jul 20, 2009

### AUMathTutor

The correct answer is 4r/3pi, if what you are after is the average y-coordinate. This can be calculated fairly easily by doing this:

(1/A) S[y*2sqrt(1-y^2)dy] from 0 to 1.

I think you are confusing a semicircular area with a semicircular arc. Both appear on the Wikipedia page with centroids. The excerpt you posted clearly refers to the case of a semicircular arc, not an area.