# Do Now 1/11/12 Take out your HW from last night. Text p. 166, #1-19 all, 23 &24 Text p. 166, #1-19 all, 23 &24 Copy HW in your planner. Text p. 170, #1-11.

## Presentation on theme: "Do Now 1/11/12 Take out your HW from last night. Text p. 166, #1-19 all, 23 &24 Text p. 166, #1-19 all, 23 &24 Copy HW in your planner. Text p. 170, #1-11."— Presentation transcript:

Do Now 1/11/12 Take out your HW from last night. Text p. 166, #1-19 all, 23 &24 Text p. 166, #1-19 all, 23 &24 Copy HW in your planner. Text p. 170, #1-11 all, 14-16 all Text p. 170, #1-11 all, 14-16 all In your journal, tell whether the figures are similar. 59° 35° 86° 119° 55° 107° 79° 107° 80° 135° 38°

Try it out Tell whether the figures are similar. 59° 35° 86° 119° 55° 107° 79° 107° 80° 135° 38° NP QS = ? NO QR = ? PO RS 7 14 4848 6 12 1212 1212 1212 = ? = ? = ? = ? Similar Not similar; corresponding angles do not have equal measures

Homework Text p. 166, #1-19 all, 23 &24 1) similar 2) not similar 3) similar 4) not similar 5) not similar 6) similar 7) similar 8) not similar 9) No, corresponding angles are not equal 10) 4 in. X 6 in., 16 in. X 24 in. 11) similar 12) not similar 13) yes 14) no 15) yes 16) yes 17) no 18) no 19) no 23) C 24) No

Objective SWBAT use similar figures to find unknown measures

Section 4.4 “Similar Figures” Similar Figures Two figures are SIMILAR FIGURES if they have the same shape but not necessarily the same size. The symbol ~ indicates two figures are similar. Two figures are similar if: 1). The measures of their corresponding angles are equal 2). The ratios of the lengths of their corresponding sides are proportional (equal ratios)

Crossmultiply Section 4.5 “Using Similar Figures” Given ABC ~ JKL, find x and y. Angle B corresponds to Angle K y = 103°

Given ABCD ~ GHIJ, find HJ. G H IJ AB CD 30 12 x 16 Cross multiply

C A B b a 32 32 F D E 20 20 35 40 Given ABC ~ DEF, find a. Given ABC ~ DEF, find b.

C A B Y Z X 20 20 g 25 25 24 24 40 40 f Given ABC ~ XYZ, find g and f.

Indirect Measurement the method of using proportions to find an unknown length or distance in similar figures

Indirect Measurements You measure the shadow of a telephone pole to be 24 ft. The shadow of a 5ft-tree is 4 ft. How tall is the telephone pole? S H s h

Indirect Measurements To estimate the height of the Transco Tower in Houston, TX, you measure its shadow to be about 55m. The shadow of a 50m flagpole is about 10m. Estimate the height of the Transco Tower. S H s h

City officials want to know the height of a traffic light. Estimate the height of the traffic light. 27.25 15 = 48.75 h Write a proportion. 27.25h = 731.25 The traffic light is about 27 feet tall. 27.25 ft 48.75 ft h ft Cross multiply. h ≈ 27 ftDivide each side by 27.25 to isolate the variable. Indirect Measurements

Homework NJASK7 Prep Text p. 170, #1-11 all, 14-16 all Text p. 170, #1-11 all, 14-16 all

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