# Reflection

Reflections are everywhere ... in mirrors, glass, and here in a lake.
... what do you notice ?

Every point is the same distance from the central line !

... and ...

The reflection has the same size as the original image.

The central line is called the Mirror Line:

## Can A Mirror Line Be Vertical?

Yes. Here my dog "Flame" shows a Vertical Mirror Line (with a bit of photo editing).

In fact Mirror Lines can be in any direction.
Imagine turning the top image in different directions:

A reflection is a flip over a line

### You can try reflecting some shapes about different mirror lines here:

images/reflect.js

## "How Do I Do It Myself?"

Just approach it step-by-step. For each corner of the shape:

1. Measure from the point to the mirror line (must hit the mirror line at a right angle)
2. Measure the same distance again on the other side and place a dot.
3. Then connect the new dots up!

## Labels

It is common to label each corner with letters, and to use a little dash (called a Prime) to mark each corner of the reflected image.

Here the original is ABC and the reflected image is A'B'C'

## Some Tricks

### X-Axis

When the mirror line is the x-axis
we change each (x,y) into (x,−y)

### Y-Axis

When the mirror line is the y-axis
we change each (x,y) into (−x,y)

### Fold the Paper

And when all else fails, just fold the sheet of paper along the mirror line and then hold it up to the light !

6716, 6717, 3346, 3344, 3345, 3347, 5152, 5153, 841, 842