Published online by Cambridge University Press: 26 February 2010
The purpose of this paper is to prove two integralgeometric formulae for convex bodies. Our results are expressed in terms of integrals with respect to the rigid-motion-invariant measure μd, r on the space ℰ(d, r) of all r-dimensional affine flats in d-dimensional Euclidean space Ed. Rolf Schneider, in an unpublished note [6], has shown that for a convex polytope P in Ed and 1 ≤ r ≤ d – 1 one has
where ηr(P) is the sum of the contents of the r-dimensional faces of P, ηo(Ed–r ∩ P) is the number of vertices of the (d – r)-dimensional section Ed–r ∩ P, and α(r) is the content of the r-dimensional unit ball.