Final answer:
The most important method to see the sides and rear for vehicles is using mirrors. Diverging mirrors are often used in rearview mirrors to allow a wider field of view, despite making objects look smaller and more distant. At least two mirrors angled correctly are needed to see the back of one's head.
Step-by-step explanation:
The most important way to see the sides and rear of a vehicle is typically through the use of mirrors. Mirrors provide a direct and reliable way to view these areas. However, modern technology has introduced other methods such as using cameras, sensors, and blind spot detection systems. Each of these methods has its advantages. Cameras can provide a clear image of what is behind the vehicle, sensors can alert to unseen hazards, and blind spot detection systems can specifically alert you to vehicles in your blind spot. Nevertheless, mirrors remain fundamental for driving and are legally required on most vehicles.
With regard to rearview mirrors, diverging mirrors are often used because they have a wider field of view than flat mirrors, allowing drivers to see more of the road behind them. The primary disadvantage of diverging mirrors compared to flat ones is that they can make objects appear smaller and further away than they actually are, which can sometimes lead to misjudgment of distance and speed.
To see the back of one's head using mirrors, an arrangement of at least two mirrors is necessary, positioned at an angle to each other so that the reflection of the back of the head can be seen in the second mirror.