Posted by Gene E. Bloch on 04/26/06 18:02

On 4/26/2006, afn03488@afn.org posted this:
> Gene E. Bloch wrote:
>
>> If you recall the formula for the area of a circle, it is A = 4 pi
>> r-squared.
>
> As I recall, the area of a circle is just pi * r-squared
>
>> Thus a circle where r = 1, called a unit sphere,
>
> How does a planer shape become a solid? It is a unit circle, not a unit
> sphere.
>
>> has an area of 4 pi,
>
> No, it has an area of pi. Where did you find this factor of four?
> Are you confused with the formula for the volume of a sphere
> which is 4/3 * pi r-cubed

Caught in a typo again :-)

The first two references to "circle" were supposed to read "sphere",
which should have been clear from the context...and should have been
typed correctly by the poster (me).

What I was discussing has nothing to do with volume.

Here's a corrected version of the mistyped paragraph:

"If you recall the formula for the area of a sphere, it is A = 4 pi
r-squared. Thus a sphere where r = 1, called a unit sphere, has an area
of 4 pi, and the area of an arbitrary shape on the surface of a unit
sphere is its angle in steradians. Thus, 4 pi steradians means all
directions, up, down, left, right, forward, behind; so, it is the
entire world surrounding you."

That should help any non-geometers who read my erroneous post :-)

Gino

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

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