# Cross sectional area (NOT A QUESTION)

1. Jun 5, 2010

### moonman239

Just for those who don't know a thing about cross sectional areas, I thought I'd explain.

A cross sectional area describes the area of a flat (2-dimensional) representation of a 3-dimensional object. So if I cut a cylinder, instead of seeing two circles, I see four circles (unless there are other circles in my environment). The cross-sectional area is the area of either of the two circles.

For a cylinder or right solid, the cross-sectional area is the area of the base.
For a sphere, the cross sectional area is the area of a circle with the same radius (pi*r2).
For an ellipsoid, the cross sectional area is the area of an ellipse with the same long (a) and short (b) axes (pi*ab).

Last edited: Jun 5, 2010
2. Jun 5, 2010

### Landau

I don't know what to say. Thanks for sharing?

3. Jun 9, 2010

### theoryiscool

lol at landau's response

4. Jun 14, 2010

### moonman239

Oh, for an oblate ellipsoid (such as Earth), where lines of latitude are circular, the area is simply pi*(r^2)