# Where can mirror lines go?

Mirror lines can go anywhere.

Where are the mirror lines?

Remember the formula for a straight line is:

`y=mx+c`

(you must see and learn the section on straight lines before you proceed.)

## Verticle lines

**Example**

Draw a reflection of the following image with a mirror line on `x=3`.

**NOTE:**

For `x=3` we can work out that if:

`y=1` then `x=3`

`y=2` then `x=3`

`y=3` then `x=3` etc

If we plot this on our graph we can find the mirror line.

We can now complete the reflection.

## Horizontal lines

**Example**

Draw a reflection of the following image with a mirror line on `y=4`.

**NOTE:**

For `y=4` we can work out that if:

`x=5` then `y=4`

`x=4` then `y=4`

`x=3` then `y=4` etc

If we plot this on our graph we can find the mirror line.

We can now complete the reflection.

## Diagonal lines

**Example 1**

Draw a reflection of the following image with a mirror line on `y=x`.

**NOTE:**

For `y=x` we can work out that if:

`y=1` then `x=1`

`y=2` then `x=2`

`y=3` then `x=3` etc

If we plot this on our graph we can find the mirror line.

We can now complete the reflection.

**Example 2**

Draw a reflection of the following image with a mirror line `y=-x`.

**NOTE:**

For `y=-x` we can work out that if:

`y=1` then `x=-1` `(1=-1timesx` therefore `x=-1)`

`y=2` then `x=-2`

`y=3` then `x=-3` etc

If we plot this on our graph we can find the mirror line.

We can now complete the reflection.

## Other examples

**Example 1**

On the grid below reflect the triangle in the line A, B.

Redraw as follows:

**Example 2**

Describe the single transformation that maps A to B.

You must first describe what this is and it is a REFLECTION.

You must now find the mirror line.

This is easy because we can describe this as a mirror line along the `x` axis.

Or

If you want to get technical, it is the line `y=0`.

i.e. `x=1` then `y=0`

`x=2` then `y=0`

`x=3` then `y=0` etc

**Answer:**

This is a reflection where the mirror line is on the `x` axis.