1. Number Sense

Virginia SOL 6 - 2020 Edition

1.09 Lengths and polygons in the coordinate plane

Lesson

Remember that the coordinate plane can be used to describe the location of points in a 2D space.

By connecting 3 or more points on the coordinate plane with line segments, we can plot polygons. Plotting polygons on the coordinate plane will allow us to easily determine lengths and distances without needing a ruler.

Later we will also look at how we can transform polygons on the coordinate plane.

Consider the point $Q$`Q` plotted on the coordinate plane.

**a)** What are the coordinates of the point that is $6$6 units to the right and $8$8 units below $Q$`Q`?

**Think:** Starting at point $Q$`Q` with coordinates $\left(-4,3\right)$(−4,3), we **add** $6$6 units to the $x$`x`-coordinate (because we are moving to the **right**), and **subtract** $8$8 units from the $y$`y`-coordinate (because we are moving **downward**).

**Do:** This gives $\left(-4+6,3-8\right)=\left(2,-5\right)$(−4+6,3−8)=(2,−5).

**b) ** If point $R$`R` has the coordinates $\left(-4,-7\right)$(−4,−7), what is the distance between $Q$`Q` and $R$`R`?

**Think:** Notice that point $R$`R` has the same $x$`x`-coordinate as point $Q$`Q`. This means that the distance between the two points is given by the difference in the two $y$`y`-coordinates.

**Do: **So the distance is $3-\left(-7\right)=10$3−(−7)=10 units.

Given a set of points, we may be asked what type of shape or polygon is formed. It can be very helpful to plot the points. From there you may need to calculate side lengths by counting squares or finding the difference in coordinates.

What are the coordinates of the vertices of this quadrilateral?

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$A\left(\editable{},\editable{}\right)$

`A`(,), $B\left(\editable{},\editable{}\right)$`B`(,), $C\left(\editable{},\editable{}\right)$`C`(,), $D\left(\editable{},\editable{}\right)$`D`(,)

What is the distance between $A\left(-6,2\right)$`A`(−6,2) and $B\left(-6,-7\right)$`B`(−6,−7)?

Identify the coordinates of a point and graph ordered pairs in a coordinate plane