  In the paper a theoretical study the both the quantized energies of excitonic
states and their wave functions in gapped graphene and in monolayer of MoS2 is
presented. An integral two-dimensional Schr\"odinger equation of the
electron-hole pairing for a particles with electron-hole symmetry of reflection
is analytically solved. The solutions of Schr\"odinger equation in momentum
space in gapped graphene and in the direct band monolayer of MoS2 by projection
the two-dimensional space of momentum on the three-dimensional sphere are
found. We analytically solve an integral two-dimensional Schr\"odinger equation
of the electron-hole pairing for particles with electron-hole symmetry of
reflection and with strong spin-orbit coupling. In monolayer of MoS2 as well as
in single-layer graphene (SLG) the electron-hole pairing leads to the exciton
insulator states. Calculating an integral two-dimensional Schr\"odinger
equation of the electron-hole pairing for bilayer graphene, an exciton
insulator states with a gap 3 meV are predicted. The particle-hole symmetry of
Dirac equation of layered materials allows perfect pairing between electron
Fermi sphere and hole Fermi sphere in the valence band and conduction band and
hence driving the Cooper instability.
