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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°

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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

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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

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Objective SWBAT use similar figures to find unknown measures

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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)

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

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

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

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

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

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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

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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

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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

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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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