Video Transcript
The coordinate Plane: First
Quadrant
In this video, we will learn how to
find the 𝑥- and 𝑦-coordinates of a point in the first quadrant and locate a point
given its coordinates.
The coordinate plane is formed by a
horizontal number line called the 𝑥-axis and a vertical number line called the
𝑦-axis. Each axis crosses each other at
zero. The axis or the coordinate plane is
divided into four sectors, which are called quadrants. This sector is called the first
quadrant.
An ordered pair describes the
location of a point on the coordinate plane. The first number is called the
𝑥-coordinate, and the second number is called the 𝑦-coordinate. So, the coordinates for the pink
point marked on our coordinate plane are three, three. Let’s take a closer look at some
coordinates.
Here we go. Our coordinate plane is made up of
a horizontal number line called the 𝑥-axis and a vertical number line called the
𝑦-axis. And we know that each axis crosses
each other at zero. And we know that an ordered pair
describes the location of a point on the coordinate plane. We always write the 𝑥-coordinate
first, followed by the 𝑦.
Did you notice all the points that
have appeared on our coordinate plane? These points can be joined to make
a picture. I wonder if you can work out what
it is? We’ve joined some of the
points. Can you tell what it is yet? I bet you can tell what it is
now. Now that we’ve ready to tell you
must have spotted that this is a dog. Let’s use some coordinates to give
our dog an eye and a nose. This is where we’re going to draw
our nose using a black circle.
The 𝑥-coordinate is always the
first number in our ordered pair. If we draw a line from our point
down to the 𝑥-axis, we can see the coordinate is one. And if we do the same with the
𝑦-axis, join our point along to the axis, we can see that the 𝑦-coordinate is
seven. So, let’s draw on our nose at one,
seven. There we go.
Now, we’ve got an eye. What are the coordinates for our
dog’s eye? Let’s start by drawing a line from
our point down to the 𝑥-axis. Here we go, which is number
three. So, we know our 𝑥-coordinate is
three. Now, we need to draw a line from
our point to the 𝑦-axis. It reaches number seven. So, the coordinates, or the ordered
pair, for our dog’s eye are three, seven. Let’s practice using coordinates
now by answering some questions.
What is the 𝑥-coordinate of
point 𝐴?
In this question, we have to
write one of the coordinates for point 𝐴. We write coordinates as an
ordered pair. We usually write the
𝑥-coordinate first. This number line is called the
𝑥-axis. This is the coordinate which we
have to find. So, let’s draw a line from our
point, point 𝐴, all the way down to the 𝑥-axis. Here we go, starting at 𝐴 all
the way down to the 𝑥-axis. Our arrow is pointing to number
three. So, the 𝑥 coordinate of point
𝐴 is three.
Write the ordered pair for the
location of the monkeys.
In this question, we have to
locate the monkeys on the coordinate plane. Here they are. We’ve marked them with the pink
dot. Now, we have to write the
ordered pair. An ordered pair describes the
location of a point on the coordinate plane. The first number is called the
𝑥-coordinate, and the second number is called the 𝑦-coordinate. So, let’s start by locating the
𝑥-coordinate. To do this, we can draw a line
from our point down to the 𝑥-axis.
Now, we can see the
𝑥-coordinate is four, and we can do the same to find the 𝑦-coordinate. We start at our point and draw
a line across to the 𝑦-axis. Now, we can see our
𝑦-coordinate is five. And we need to place our
ordered pair inside brackets. The ordered pair for the
location of the monkeys is four, five.
Which point is at four,
six?
In this question, we are shown
five different points on our coordinate plane: points 𝐴, 𝐵, 𝐶, 𝐷, and
𝐸. And we have to identify the
point which is at four, six. When we see an ordered pair or
a pair of coordinates, we have to remember that the 𝑥-coordinate always comes
first followed by the 𝑦-coordinate. So, we know that number four is
the 𝑥-coordinate. If we start at four on the
𝑥-axis and draw a line going up, this will help us to identify which point is
at number four on the 𝑥-axis.
So, let’s start drawing from
four on the 𝑥-axis. Can you see which point we’re
going to reach? It looks like our point is
point 𝐸. But we need to check the
𝑦-coordinate, which is six. So, let’s find six on the
𝑦-axis and draw our line across until we reach a point. Here we go. Here’s six on the 𝑦-axis. And if we join our point along
this line, again we reach point 𝐸. The point which is at four, six
is point 𝐸.
What are the coordinates of the
missing point which would complete the square?
In this question, we have to
complete the partially drawn square, and then we have to write the coordinates
of this missing point. Let’s start by thinking about
where to draw the missing point. It would go here, let’s join up
the points to complete the square. There we go. Now, we need to write the
coordinates of this point. When we write a pair of
coordinates, we always write the 𝑥-coordinate first.
This orange line is the
𝑥-axis. We need to draw a line from our
point down to the 𝑥-axis. Now, we can see the
𝑥-coordinate is six. Let’s do the same to find the
𝑦-coordinate: draw a line from our point all the way along to the 𝑦-axis. The pink line shows our
𝑦-axis. And by drawing a line from our
point to the 𝑦-axis, we can see the 𝑦-coordinate is three. The coordinates of the missing
point which would complete the square are six, three. Our 𝑥-coordinate is six and
our 𝑦-coordinate is three.
What have we learned in this
video? We’ve learned how to find the 𝑥-
and 𝑦-coordinates of a point in the first quadrant. And we also learned how to locate a
point given its coordinates.
