2
TWO (2): The rear view mirror and left side driver's mirror. If the vehicle has no rear window, then TWO outside mirrors are required.
Side view mirrors.
To give a wider angle of view.
All state laws require vehicles to have rear view mirrors (the ones that mount to the interior windshield).
Convex mirrors are typically used on the side mirrors of vehicles. These mirrors are curved outwards, allowing for a wider field of view to help drivers see vehicles approaching from the side.
adjusting your rear view and side mirrors properly Edit: Or Installing large side mirrors
Called side mirrors. Drivers side mirror/passenger side mirror.
The side view mirrors can be heated for removing ice/snow.
Passenger side mirrors were optional. Some were mechanically (not powered) remote controlled.
On what?
If your motorcycle is old enough to have been sold new without them, you are not required to have them.