Reflection — Part 2: Invariant points, combined reflections and figures: visual lesson, ICSE Class 10 Mathematics

Lesson

Reflection, Part 2

Reflect a whole figure and it keeps its size and shape but faces the other way. Points and their images together make new figures to name and measure.

In this lesson you will

Identify the invariant points of a reflection
Combine two reflections and find a single equivalent reflection
Reflect a figure and plot it with its image on graph paper
Name the figure formed and find its area or perimeter

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image

A reflected figure is the same size and shape, but faces the other way.

Concept

What you will be able to do

Find the invariant points of a reflection
Combine two reflections into one
Reflect a figure and plot it with its image
Name the figure formed and find its area or perimeter

Concept

Invariant points

A point is invariant under a reflection if it is its own image. For a mirror line, the invariant points are exactly the points on the line. For reflection in the origin, only the origin itself is invariant.

WW′

Points on the mirror are invariant; every other point moves.

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