### Video Transcript

These lines are perpendicular. What type of angle is highlighted
in red?

The first sentence in this question
contains a really interesting word “perpendicular.” Now, we’re told that these lines
are perpendicular, but which lines is it describing? Well, if we look in the picture, we
can see two lines. We’ve got one that’s vertical that
goes up and down. And we’ve also got a horizontal
line that has been drawn from left to right. Now, what can we say about these
lines? Well, firstly, we can see that
they’re straight lines. They’re not curved at all, are
they? We can also see that these two
lines meet together. In fact, they cross over each
other, don’t they?

Now, there are lots of ways we
could draw two lines that cross over each other, like this or this. But the two lines in our picture
are interesting because they meet in a special way. When two lines are perpendicular,
we know that they meet at right angles. But imagine that we read this first
sentence and we didn’t know what the word “perpendicular” means. Can you see another clue that helps
us? This little symbol here is the
symbol for right angles. So even if we’re not quite sure
what the word “perpendicular” means, we could look at the diagram, see this little
symbol, and think to ourselves, “I know that these two lines meet at right
angles.”

Now, our question asks us, what
type of angle is highlighted in red? Can you see what this is talking
about? It’s this angle here. How could we describe this
angle? Well, because we know that these
two lines are perpendicular, we can draw little right-angle symbols at all the
places where they meet. The angle that’s shown in red is a
right angle. When two lines are perpendicular,
they meet at right angles. And that’s how we know the type of
angle that’s highlighted in red is a right angle.