There is no opposite....
Please rephrase your question.
The tail propeller keeps the helicopter straight.
"For every action there is an opposite and equal reaction." For the helicopter to make the blade move in one direction, the blade will try to make the helicopter move in the opposite direction. Since the blade tries to make the helicopter spin, something is needed to keep the helicopter from spinning. So the manufacturer puts a tail rotor on the helicopter.
It has another rotor on the tail that spins vertically and counteracts the effects of the rotor on the top. Still, a helicopter is difficult to keep balanced and helicopter pilots are very talented people!
By adjusting the speed of tail rotor, which points to the side, the pilot can turn the helicopter in flight. The main upper rotor actually plays only a minor part in making helicopter turn. The part supplying most of the control is the tail rotor. Because the main rotor is spinning in one direction, without a tail rotor, the body of the helicopter would spin around in circles in the opposite direction. The reason for this is explained in the first part of Newton's third law of motion: for every action there is an equal and opposite action. The torque generated to make the rotor turn also exerts torque on the body of the helicopter "willing" it to spin the opposite direction. However, the tail rotor spins, pushing air to the side. This creates force in the opposite direction, keeping the helicopter stable. By simply adjusting the speed of the tail rotor, the helicopter can be turned in flight.
Trim it by turning the trim knob in the opposite direction that it is spinning
A purple helicopter is a helicopter of the color purple. Really?
Everybody I know says A helicopter.
For the helicopter body to be in balance and direction to steer the helicopter.
A helicopter pilot flies a helicopter in the army.
There is no helicopter.
In their helicopter.