How can the statement be rewritten as a conditional statement in if-then form? Lines on a coordinate plane are perpendicular if they have opposite reciprocal slopes. If lines on a coordinate plane have opposite reciprocal slopes, then they are perpendicular. If lines are on a coordinate plane, then they are perpendicular. If lines are on a coordinate plane, then they have opposite reciprocal slopes. If lines have opposite reciprocal slopes and are perpendicular, then they are on a coordinate plane.