Exercise 7 Page 409

Draw the polygon. What do you need to know to be able to calculate its area?

20 square feet

Practice makes perfect

When drawing the polygon, the first thing we should notice is its shape. This polygon has four vertices, so it is a quadrilateral. Let's draw it in a coordinate plane.

Notice that the sides of the quadrilateral are vertical lines and that the top and bottom are horizontal lines. Vertical and a horizontal lines are perpendicular to each other. This means that all of the angles in the polygon are right angles and that the quadrilateral is a rectangle. We can calculate its area using the formula for the area of a rectangle. A=l w In this formula, l is the length and w is the width. We can find the measure of the length and width using the Ruler Postulate. Let's start with MN.

MN=|x_2-x_1|

SubstituteII

x_2= 6, x_1= 2

MN=| 6- 2|

SubTerm

Subtract term

MN=|4|

AbsPos

|4|=4

MN=4

The length l is 4 feet. We will find the width in the same way.

MR=|y_2-y_1|