  We measured separate cosmic-ray electron and positron spectra with the Fermi
Large Area Telescope. Because the instrument does not have an onboard magnet,
we distinguish the two species by exploiting the Earth's shadow, which is
offset in opposite directions for opposite charges due to the Earth's magnetic
field. We estimate and subtract the cosmic-ray proton background using two
different methods that produce consistent results. We report the electron-only
spectrum, the positron-only spectrum, and the positron fraction between 20 GeV
and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV
range. The three new spectral points between 100 and 200 GeV are consistent
with a fraction that is continuing to rise with energy.
