  We report the results of a study of superconducting proximity effects in
clean Ferromagnet/Ferromagnet/Superconductor (${\rm F_1F_2S}$)
heterostructures, where the pairing state in S is a conventional singlet
s-wave. We numerically find the self-consistent solutions of the Bogoliubov-de
Gennes (BdG) equations and use these solutions to calculate the relevant
physical quantities. By linearizing the BdG equations, we obtain the
superconducting transition temperatures $T_c$ as a function of the angle
$\alpha$ between the exchange fields in $\rm F_1$ and $\rm F_2$. We find that
the results for $T_c(\alpha)$ in ${\rm F_1F_2S}$ systems are clearly different
from those in ${\rm F_1 S F_2}$ systems, where $T_c$ monotonically increases
with $\alpha$ and is highest for antiparallel magnetizations. Here,
$T_c(\alpha)$ is in general a non-monotonic function, and often has a minimum
near $\alpha \approx 80^{\circ}$. For certain values of the exchange field and
layer thicknesses, the system exhibits reentrant superconductivity with
$\alpha$: it transitions from superconducting to normal, and then returns to a
superconducting state again with increasing $\alpha$. This phenomenon is
substantiated by a calculation of the condensation energy. We compute, in
addition to the ordinary singlet pair amplitude, the induced odd triplet
pairing amplitudes. The results indicate a connection between equal-spin
triplet pairing and the singlet pairing state that characterizes $T_c$. We find
also that the induced triplet amplitudes can be very long-ranged in both the S
and F sides and characterize their range. We discuss the average density of
states for both the magnetic and the S regions, and its relation to the pairing
amplitudes and $T_c$. The local magnetization vector, which exhibits reverse
proximity effects, is also investigated.
