  The measurements of gamma-ray fluxes and cosmic-ray electrons and positrons
in the energy range from 100 MeV to several TeV, which will be implemented by
the specially designed GAMMA-400 gamma-ray telescope, concern with the
following broad range of science topics. Searching for signatures of dark
matter, surveying the celestial sphere in order to study gamma-ray point and
extended sources, measuring the energy spectra of Galactic and extragalactic
diffuse gamma-ray emission, studying gamma-ray bursts and gamma-ray emission
from the Sun, as well as high precision measuring spectra of high-energy
electrons and positrons, protons and nuclei up to the knee. To clarify these
scientific problems with the new experimental data the GAMMA-400 gamma-ray
telescope possesses unique physical characteristics comparing with previous and
present experiments. For gamma-ray energies more than 100 GeV GAMMA-400
provides the energy resolution of ~1% and angular resolution better than 0.02
deg. The methods developed to reconstruct the direction of incident gamma
photon are presented in this paper, as well as, the capability of the GAMMA-400
gamma-ray telescope to distinguish electrons and positrons from protons in
cosmic rays is investigated.
