Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
2. Areas of Trapezoids, Rhombuses, and Kites
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Exercise 32 Page 627

Recall the classification of quadrilaterals. You can begin by finding the slopes of the sides.

18 units squared

Practice makes perfect

Let's identify the coordinates of the given quadrilateral.

First, we need to determine the most precise name for our quadrilateral. Then we can find its area.

Name

To determine the most precise name for our quadrilateral, let's review the classification of quadrilaterals.
Quadrilateral Definition
Parallelogram Both pairs of opposite sides are parallel
Rhombus Parallelogram with four congruent sides
Rectangle Parallelogram with four right angles
Square Parallelogram with four congruent sides and four right angles
Trapezoid Quadrilateral with exactly one pair of parallel sides
Isosceles Trapezoid Trapezoid with legs that are congruent
Kite Quadrilateral with two pairs of consecutive sides congruent and no opposite sides congruent

Now, let's find the slopes of the sides using the Slope Formula.

Side Slope Formula Simplified
Slope of QR: ( 0,0), ( 2,3) 3- 0/2- 0 3/2
Slope of RS: ( 2,3), ( 6,0) 0- 3/6- 2 - 3/4
Slope of ST: ( 6,0), ( 2, -3) -3- 0/2- 6 3/4
Slope of TQ: ( 2, -3), ( 0,0) 0-( -3)/0- 2 - 3/2

We have found that the quadrilateral has no parallel sides. Therefore, we need to continue by finding the lengths of its sides. For that we will use the Distance Formula.

Side Distance Formula Simplified
Length of QR: ( 0,0), ( 2,3) sqrt(( 2- 0)^2+( 3- 0)^2) sqrt(13)
Length of RS: ( 2,3), ( 6,0) sqrt(( 6- 2)^2+( 0- 3)^2) 5
Length of ST: ( 6,0), ( 2, -3) sqrt(( 2- 6)^2+( -3- 0)^2) 5
Length of TQ: ( 2, -3), ( 0,0) sqrt(( 0- 2)^2+( 0-( -3))^2) sqrt(13)

Our parallelogram has two pairs of consecutive sides congruent and no opposite sides congruent. Therefore, the most precise name for this quadrilateral is a kite.

Area

Next we will use the formula for the area of a kite. A=1/2d_1d_2 In this case we need to find the length of the diagonals, d_1=QS and d_2=RT.

Side Distance Formula Simplified
Length of QS: ( 0,0), ( 6,0) sqrt(( 6- 0)^2+( 0- 0)^2) 6
Length of RT: ( 2,3), ( 2, -3) sqrt(( 2- 2)^2+( - 3- 3)^2) 6

Let's substitute these values into the formula to find A. A= 1/2(6)(6) ⇔ A=18 The area of our kite is 18 units squared.