If the coordinate velocity v dx/dt in units of c is (e 2 − 1)/(e 2 + 1) ≅ 0.761, what is the velocity angle η in i-radians?
create table table_15314901_1 (velocity_angle_η_in_i_radians varchar, coordinate_velocity_v_dx_dt_in_units_of_c varchar, PRIMARY KEY (velocity_angle_η_in_i_radians))
select velocity_angle_η_in_i_radians from table_15314901_1 where coordinate_velocity_v_dx_dt_in_units_of_c = "(e 2 − 1)/(e 2 + 1) ≅ 0.761"