Harmonic Parameter
The harmonic parameter of a polyhedron is the weighted mean of the distances 👁 d_i
from a fixed interior point to the
faces, where the weights are the areas 👁 A_i
of the faces, i.e.,
This parameter generalizes the identity
| 👁 (dV)/(dr)=S, |
(2)
|
where 👁 V
is the volume, 👁 r
is the inradius, and 👁 S
is the surface area, which
is valid only for symmetrical solids, to
| 👁 (dV)/(dh)=S. |
(3)
|
The harmonic parameter is independent of the choice of interior point (Fjelstad and Ginchev 2003). In addition, it can be defined not only for polyhedron, but any 👁 n
-dimensional solids that have 👁 n
-dimensional content 👁 V
and 👁 (n-1)
-dimensional content 👁 S
.
Expressing the area 👁 A
and perimeter 👁 p
of a lamina in terms of 👁 h
gives the identity
| 👁 (dA)/(dh)=p. |
(4)
|
The following table summarizes the harmonic parameter for a few common laminas. Here, 👁 r
is the inradius of a given lamina, and 👁 a
and 👁 b
are the side lengths of a rectangle.
Expressing 👁 V
and 👁 S
for a solid in terms of 👁 h
then gives the identity
| 👁 h=(3V)/S. |
(5)
|
The following table summarizes the harmonic parameter for a few common solids, where some of the more complicated values are given by the polynomial roots
👁 h_4
is root of a high-order polynomial, and
See also
Surface Area, VolumeExplore with Wolfram|Alpha
More things to try:
References
Fjelstad, P. and Ginchev, I. "Volume, Surface Area, and the Harmonic Mean." Math. Mag. 76, 126-129, 2003.Referenced on Wolfram|Alpha
Harmonic ParameterCite this as:
Weisstein, Eric W. "Harmonic Parameter." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/HarmonicParameter.html
