Distance between two lines

Imagine you have two straight lines. They look like two long roads that go on forever. If you want to know how far apart these roads are, we measure the distance between them.

If you look at the roads from a bird’s eye view (like a map), you might notice that the two roads look like they’re parallel to each other - which means they never meet. But even if two roads never meet, they might still be closer to each other in some parts than in others.

So, to find the distance between two parallel roads that never meet, you can draw a line (like a third road) that goes straight down and touches one of the roads, and then draw a line from there that touches the other road. We call this line the “perpendicular” because it meets the other two at 90 degree angles.

The distance between the two parallel roads is the length of this perpendicular line, measured from where it touches one road to where it touches the other. It’s like measuring how long a piece of string is, except in this case it’s a straight line.

Now, this may not always work out exactly, because sometimes the roads might be really wide and the perpendicular line might not touch the other road exactly on the edge. But we can use a special math formula to find the distance between two parallel roads even if they’re not perfectly straight and even if they’re not parallel anymore. All you have to do is remember the first step: draw the perpendicular line.