  In this paper, we show how the mixing angles of the standard parameterization
add when multiplying the quark and leptonic mixing matrices, i.e., we derive
explicit sum rules for the quark and leptonic mixing angles. In this
connection, we also discuss other recently proposed sum rules for the mixing
angles assuming bimaximal fermion mixing. In addition, we find that the present
experimental and phenomenological data of the mixing angles naturally fulfill
our sum rules, and thus, give rise to bilarge or bimaximal fermion mixing.
