 There are four types of transformation that we learn about in maths. In this video we're going to learn about reflections in more detail. Look in a mirror and you see your reflection. In maths it's pretty much the same thing, however instead of a mirror there's a mirror line. The mirror line is also known as the axis of reflection. See how the triangle ABC and the reflected triangle are equal distances away from the mirror line. So point A is three squares away, so the reflected point must also be three squares away. Point B is also three squares away, so then count another three squares from the reflected point. And point C is just one square away. So only one square. Reflecting shapes is all about counting squares. Did you notice that the starting point is called A and then the reflected point is called A apostrophe? Another key thing to notice about reflections is that they are always perpendicular to the mirror line, so we count squares at right angles to the mirror line. Which is easy here because the mirror line is vertical and we can count squares horizontally. But now we have a diagonal mirror line. See how the distances now also have to be diagonal. So that we cross the mirror line at right angles. Here's a little tip. If it's difficult for you to envisage the shape being perpendicular to the mirror line, you can rotate the page so that the mirror line appears vertical. So let's reflect the rectangle. So point A, we've gone diagonally across two squares. So we go across another two squares. Point B is three squares, and another three squares. Point C is one and a half, so one and a half the other side. So reflected point D must be here to make the final shape. What happens when the starting shape overlaps the mirror line? We still do exactly the same thing, counting squares to the mirror line, making sure we cross the mirror line at right angles, perpendicular. The only difference is that the point C needs to be reflected onto the other side of the mirror line. Give these questions a go, pause the video, work them out, and then click play when you're ready. Did you get them right? Don't skip corners. Make sure you count out each new point. So there we have the two fundamental rules for reflecting a shape. Must always be perpendicular to the mirror line, and the reflected shapes are equal distant from the mirror line.