  We completely calculate the $RO(G)$-graded coefficients of ordinary
equivariant cohomology where $G$ is the dihedral group of order $2p$ for a
prime $p>2$ both with constant and Burnside ring coefficients. The authors
first proved it for $p=3$ and then the second author generalized it to
arbitrary $p$. These are the first such calculations for a non-abelian group.
