CREATE TABLE table_15314901_1 (velocity_angle_η_in_i_radians VARCHAR(255), coordinate_velocity_v_dx_dt_in_units_of_c VARCHAR(255))
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?
    
SQL: 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"