  We investigate the linear tidal perturbation of a viscous Keplerian disk by a
companion star orbiting in a plane inclined to the disk. We consider m=1
perturbations with odd symmetry with respect to the z=0 midplane. Since the
response of a viscous disk is not in phase with the perturbing potential, a
tidal torque is exerted on the disk, resulting in a decrease of its angular
momentum. This tidal torque is found to be comparable to the horizontal viscous
stress acting on the background flow when the perturbed velocities in the disk
are on the order of the sound speed. If these velocities remain subsonic, the
tidal torque can exceed the horizontal viscous stress only if the viscous
parameter \alpha which couples to the vertical shear is larger than that
coupled to the horizontal shear. In protostellar disks, bending waves are found
to propagate deep into the disk inner parts. If the waves are reflected at the
center, resonances occur when the frequency of the tidal waves is equal to that
of some free normal global bending mode of the disk. If such resonances exist,
tidal interactions may then be important even when the binary separation is
large. Out of resonance, the torque associated with the secular perturbation is
generally much larger than that associated with the finite frequency
perturbations. As long as the waves are damped before they reach the center,
the torque associated with the finite frequency perturbations does not depend
on the viscosity. These calculations are relevant to disks around young stars
and maybe also to disks in X-ray binary systems. (abridged)
