Reflections Day 119 Learning Target: Students can represent transformations in the plane; describe transformations as functions that take points in the plane as inputs and give other points as outputs. Compare transformations that preserve distance and angle to those that do not (e.g., translation versus horizontal stretch).

Reflections…

A reflection “flips” an object and can be seen in water, in a mirror, in glass, or in a shiny surface.  An object and its reflection have the same shape and size, but the figures face in opposite directions.  In a mirror, for example, right and left are switched.

The line (where a mirror may be placed) is called the line of reflection.  The distance from a point to the line of reflection is the same as the distance from the point's image to the line of reflection. A reflection can be thought of as a "flipping" of an object over the line of reflection. The object ABCD is being reflected over the x-axis.

Reflect across the x-axis Change the sign of the y-value

Reflect across the x-axis

Reflect across the y-axis Change the sign of the x-value

Reflect across the y-axis

Reflect across y = x Swap x and y

Reflect across y = x

Reflect across y = -x Swap and change both signs

Reflect across y = -x

Reflections by Hand & Reflections Using a Mira Classwork… Reflections by Hand & Reflections Using a Mira