What must be provided to describe a reflection?

To describe a reflection accurately, it is essential to provide the equation of the mirror line. The mirror line acts as the axis of reflection, determining how and where the shape will be mirrored. This line essentially defines the "boundary" over which the reflection occurs, guiding the transformation of each point of the original shape to its corresponding point in the reflected shape.

When you have the equation of the mirror line, you can use it to find how far each point of the original shape is from the line and then locate the reflected point on the opposite side of the line, at an equal distance. Without this key information, it's impossible to visualize or calculate the reflected shape accurately.

Knowing the coordinates of the shape, the center of the figure, or the angle of incidence could provide additional details about the object or the reflection process, but none of these options can substitute for the fundamental requirement of knowing where the mirror line is positioned in relation to the object being reflected.