TODAY IN GEOMETRY…

Review: Arc Length

Learning Target : 11.3 You will use ratios to find areas of similar figures

Independent practice

CH.10 TEST – THURSDAY/FRIDAY!

REVIEW: Find

2(5 𝑥−11)1. Arc is twice the inscribed arc.

2. Angles around a circle add to

3.

AREAS OF SIMILAR POLYGONS:

𝑏𝑎

Polygon I Polygon II

𝑃 𝑜𝑙𝑦𝑔𝑜𝑛𝐼 𝑃𝑜𝑙𝑦𝑔𝑜𝑛𝐼𝐼

RATIO OF SIDES:POLYGON I

POLYGON II¿ 𝑎𝑏

RATIO OF AREAS:POLYGON I

POLYGON II¿ 𝑎2

𝑏2

RATIO OF PERIMETERS:POLYGON I

POLYGON II¿ 𝑎𝑏

EXAMPLE: In the diagram, . Find the indicated ratio.

a. Ratio (red to blue) of the perimeters

b. Ratio (red to blue) of the areas

a. Ratio of Perimeter 812

¿23

b. Ratio of Areas 22

32¿49

PRACTICE: In the diagram, . Find the indicated ratio.

a. Ratio of the perimeters

b. Ratio of the areas

a. Ratio of Perimeter 1810

¿95

b. Ratio of Areas 92

52¿8125

Figure 1 Figure 2

1810

EXAMPLE: Rectangles I and II are similar. The perimeter of Rectangle I is 66 inches. Rectangle II has a perimeter of 110 inches and an area of . Find the area of Rectangle I.

1. Ratio of Perimeter

2. Ratio of Areas

3. Set up proportions of areas

Cross multiply

Divide

66110

¿35

32

52¿925

925

𝑥700

EXAMPLE 2: Find the ratio of the perimeter (red to blue) and area. Then find the unknown area.

1. Ratio of Perimeter

2. Ratio of Areas

3. Set up proportions of areas

Cross multiply

Divide

1612

¿43

42

32¿169

169

64𝑥

16 𝑓𝑡 12 𝑓𝑡𝐴=64 𝑓𝑡2

PRACTICE: Find the ratio of the perimeter (red to blue) and area. Then find the unknown area.

1. Ratio of Perimeter

2. Ratio of Areas

3. Set up proportions of areas

Cross multiply

Divide

1014

¿57

52

72¿2549

2549

𝑥441

10 𝑓𝑡 14 𝑓𝑡

𝐴=441 𝑓𝑡2

PRACTICE: Find the ratio of the perimeter (red to blue) and area. Then find the unknown area.

1. Ratio of Perimeter

2. Ratio of Areas

3. Set up proportions of areas

Cross multiply

Divide

128

¿32

32

22¿94

94

108𝑥

12 𝑓𝑡 8 𝑓𝑡𝐴=108 𝑓𝑡 2

HOMEWORK #10:

Pg. 740: 3-14

If finished, work on other assignments:

HW #1: Pg. 655: 3-20, 24-26, 30HW #2: Pg. 661: 3-14, 17, 23HW #3: Pg. 667: 3-15HW #4: Pg. 676: 3-16 Pg. 679: 40-46HW #5: Pg. 683: 3-13HW #6: Pg. 692: 3, 4, 6, 9-14HW #7: Pg. 702: 3-25HW #8: Pg. 749: 3-7, 11-13, 15-23HW #9: Pg. 758: 11-17, 26-31