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## Topic A: Basic constructions

Current time:0:00Total duration:1:26

# Geometric constructions: perpendicular bisector

CCSS Math: HSG.CO.D.12

## Video transcript

We're asked to construct
a perpendicular bisector of the line segment AB. So the fact that
it's perpendicular means that this line will
make a 90-degree angle where it intersects with AB. And it's going to
bisect it, so it's going to go halfway in between. And I have at my disposal
some tools I can put out. I can draw things
with a compass, and I can add a straight edge. So let's try this out. So let me add a compass. And so this is a
virtual compass. So in a real compass, it's
one of those little metal things where you can
pivot it on one point, and you can draw a
circle of any radius. And so here I'm going to draw--
I'm going to center it at A. And I'm going to make the radius
equal to the length of AB. Now I'm going to add another
circle with my compass. And now, I'm going
to center it at B and make the radius equal to AB. And now, this
gives me two points that I can actually use to
draw my perpendicular bisector. If I connected this
point and this point, it is going to bisect
AB, and it's also going to be perpendicular. So let's add a
straight edge here, so this is to draw a line. So I'm going to draw a
line between that point and that point right over there. And let me scroll
down, so you can look at it a little bit clearer. So there you go. That's my construction. I've made a perpendicular
bisector for segment AB. Check my answer. We got it right.