Transformation of the Geometry of Reflection (Reflection)


Reflection is a transformation that pairs each point on the plane using the mirror image properties of the points to be moved. (Herynugroho, et al, 2009: 184)


The three main properties of reflection are:


The distance from the mirror point is the same as the distance between the image point from the mirror.

A shape that is reflected will be congruent with the image.

The angles produced by the mirror with the connecting lines of each point to its image are right angles. (Sartono, 2006: 196).


If we analize using a mirror, something like this:

To better understand the meaning of reflection, consider the following simulation:


Consider the following simulation too:

The equation for the transformation of the reflection to the X axis

     If point A (a, b) is reflected on the X axis, then the result of the reflection or image of point A '(a', b ') is obtained with the transformation equation for the reflection is


     The reflection transformation can be written as follows. (Tampomas Husein, 2007: 249)


Problems example :

• Point P (-5, 7) is mirrored to the X axis. Determine the image!


Answer:

     The image point from point P (-5, 7) by reflection on the X axis is P '(- 5, 7).


The equation for the transformation of the reflection on the Y axis

     If point A (a, b) is reflected on the Y axis, then the result of the reflection or image of point A '(a', b ') is obtained with the transformation equation for the reflection is


     The reflection transformation can be written as follows. (Tampomas Husein, 2007: 249)


Problems example :


• Triangle ABC with A (2, -3), B (-5, 2), and C (5,7) mirrored to the Y axis. Find the image!


Answer:


The image point from point A (2, -3) by reflection on the Y axis is A '(- 2, -3).


The image point from point B (-5, 2) by reflection on the Y axis is B '(5, 2).


The image point from point C (5, 7) by reflection on the Y axis is C '(5, 7).

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