Conic intrinsic volumes of Weyl chambers

We give a new, direct proof of the formulas for the conic intrinsic volumes of the Weyl chambers of types $A_{n-1}, B_n$ and $D_n$. These formulas express the conic intrinsic volumes in terms of the Stirling numbers of the first kind and their $B$- and $D$-analogues. The proof involves an explicit determination of the internal and external angles of the faces of the Weyl chambers.