Lesson 11-2 Lesson 11-2 Day 2Day 2

Area of Trapezoids and Area of Trapezoids and RhombiRhombi

Area of Trapezoids & RhombiArea of Trapezoids & Rhombi

Trapezoid AreaA = ½* h* (b1 + b2) h is height (altitude)b1 and b2 are bases (JK & LM)(bases are parallel sides)

Rhombus AreaA = ½ * d1 * d2

d1 and d2 are diagonals

A B

C D

h

b1

b2

J K

L M

N

d1

d2

Example 1Example 1

h

20

12

J K

LM

N60°

14

Find the area of trapezoid JKLM

Trapezoid DEFG has an area of 120 square feet. Find the height of DEFG.

Example 2

Example 3Example 3A B

CD5

Find the area of rhombus ABCD

5

4 3

Is there another way to find the area of a rhombus?

Rhombus RSTU has an area of 64 square inches. Find US if RT = 8 inches.

Example 4

b. Trapezoid QRST has an area of 210 square yards. Find the height of QRST.

a. Rhombus ABCD has an area of 81 square centimeters. Find BD if AC = 6 centimeters.

Example 5

INTERIOR DESIGN This window hanging is composed of 12 congruent trapezoidal shapes. The total area of the design is 216 square inches. Each trapezoid has bases of 4 and 8 inches. Find the height of each trapezoid.

Example 6

Example 7Example 7

Find the area of the trapezoid given Find the area of the trapezoid given the following coordinates (-1,8), the following coordinates (-1,8), (5,8), (3,4), and (1,4).(5,8), (3,4), and (1,4).

Example 8Example 8 Find the area of the rhombus with Find the area of the rhombus with

the following coordinates (-4,3), (-the following coordinates (-4,3), (-2,4), (0,3) and (-2,2)2,4), (0,3) and (-2,2)

Summary & HomeworkSummary & Homework Summary:Summary:

The formula for the area of a triangle can The formula for the area of a triangle can be used to find the areas of many be used to find the areas of many different figuresdifferent figures

Congruent figures have equal areasCongruent figures have equal areas

Homework:Homework: pg 605 (10, 11, 15-18, 30-33)pg 605 (10, 11, 15-18, 30-33)