## The Line of Reflection

The line of reflection is a mirror line. It is the line a shape is reflected in. The image below shows a shape reflected in a line of reflection.## How to Describe a Reflection

Describing a reflection is easy.## Question

Describe how the light blue shape below has been reflected to make the dark blue shape.## Step-by-Step:

## 1

Find a point on the shape and the corresponding point on its reflection.We will choose point

**A**on the shape. Point**A'**is the corresponding point on the reflection.## 2

Join the points with a line.

## 3

Mark the half way point of this line.

## 4

Find another point on the shape and the corresponding point on its reflection.We will choose point

**B**on the shape. Point**B'**is the corresponding point on the reflection.## 5

Join the points with a line.

## 6

Mark the half way point of this line.

## 7

Join the half way points with a line.

## 8

Find the equation of the line.
The equation of the line is

**y = x + 2**.## Answer:

The shape has been reflected in the line**y = x + 2**:

## What Is a Reflection?

A reflection flips a shape so that it becomes a mirror image of itself. A reflection is a type of transformation.## How to Find the Equation of a Line

It is useful to say what the equation of the line of reflection is. The equation of a line can be given in slope-intercept form:
y =

**m**x +**c****m**is the slope (the steepness) of the line.**c**is the y-intercept of the line: where the line crosses the y-axis.

- The line goes up by
**1**unit for every**1**unit it goes across. The line has a slope of**1**. - The line crosses the y-axis at 2. It has a y-intercept of
**2**.

y = **1**x + **2** ∴

**y = x + 2**

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