Cyclohexene is treated with bromine, with methanol as the solvent in large excess. The major product is

Bromine forms a cyclic bromonium ion. The solvent methanol, present in huge excess, attacks it from the face opposite to Br (anti opening), so Br and OCH3 end up trans. Bromide attack would give trans-1,2-dibromocyclohexane, which is minor here. A geminal 1,1-product cannot form from a bromonium ion.