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Learn about similar polygons and their properties, including congruent angles and proportional sides. Find the scale factor and solve for variables in similarity statements.
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Unit 5 Lesson 2 Notes Use Similar Polygons
Similar Polygons: ~ • Corresponding angles are congruent • Corresponding sides are proportional
Scale Factor: The ratio of the all of the sides of similar figures.
1. List all pairs of congruent angles for the figures. Then write the ratios of the corresponding sides in a statement of proportionality. B E A D Angles: _______ _______ _______ Sides: ___________________ C F
1. List all pairs of congruent angles for the figures. Then write the ratios of the corresponding sides in a statement of proportionality. Angles: _______ _______ _______ _______ Sides: __________________________ C M D J E K F L
Angles Sides ________ _______ ________ _______ ________ _______ Similar: YES or NO Similar Statement: ___________________ Scale Factor: ________ 2. Determine whether the polygons are similar. If they are, write a similarity statement and find the scale factor from triangle B to triangle A. P M T L O N PTO ~ MLN
Angles Sides ________ _______ ________ _______ ________ _______ Similar: YES or NO Similar Statement: ___________________ Scale Factor: ________ 2. Determine whether the polygons are similar. If they are, write a similarity statement and find the scale factor from triangle B to triangle A. B A
3. The polygons are similar. Find the values of the variables. 1 2 6x = 48 x = 8 x = 8
3. The polygons are similar. Find the values of the variables. 6m = 66 m = 11
3. The two triangles are similar. Find the values of the variables. 6m = 66 12n = 48 m = 11 n = 4
4. The two figures are similar. Find the scale factor of their sides. Then find the ratios of their perimeters. What do you notice? 18 12 12 8 36 24 6 4 Scale Factor: They are the same! Ratio of Perimeters:
ratio If two polygons are similar, then the ______ of their __________ is equal to the ratios of their corresponding ____ lengths perimeters side
5. The ratio of one side of a picture to the corresponding side of a larger picture is 2:7. The perimeter of the smaller picture is 16 inches. Find the perimeter of the larger picture. 1 8 x 16 2x = 112 2 7 x = 56in x = 56in
6. In the diagram, WXYZ ~ BCDE. • Find the scale factor of WXYZ to BCDE.
6. In the diagram, WXYZ ~ BCDE. b. Find the value of XY. 3 4.5 4.5 2XY = 9 XY = 4.5
6. In the diagram, WXYZ ~ BCDE. c. Find mC. 3 mC = 117° 4.5 4.5
6. In the diagram, WXYZ ~ BCDE. d. Find the perimeter of WXYZ. 3 16 x 1 8 4.5 4.5 2x = 48 x = 24 x = 24
AA Similarity (AA ~) Two triangles are similar if two of their corresponding angles are congruent.
Use the diagram to complete the statement. 5. x = _______ x 12x = 160 40 3 x =
Use the diagram to complete the statement. 6. y = _______ 8 12y = 128 32 3 y =
7. Determine whether the triangles are similar. If they are, explain why andwrite a similarity statement. 77° 55° YES or NO Postulate: ______________ Similarity: _____________ AA~ ABC ~ DEF
7. Determine whether the triangles are similar. If they are, explain why andwrite a similarity statement. 47° YES or NO Postulate: ______________ Similarity: _____________ 31°
7. Determine whether the triangles are similar. If they are, explain why andwrite a similarity statement. YES or NO Postulate: ______________ Similarity: _____________ AA~ ABC ~ EDC
7. Determine whether the triangles are similar. If they are, explain why andwrite a similarity statement. YES or NO Postulate: ______________ Similarity: _____________ AA~ SRV ~ TRU
8. Find the length of BC. 7x = 20 20 7 x =
9. Find m. 1 3 70m = 13650 m = 195 m = 195
10. Find the value of x. 4x = 70 x = 17.5 x 5 14 4 10 4
10. Find the value of x. 8 8x = 56 8 x = 7 14 4 4 6 x x
11. In order to estimate the height, h, of a flag pole, a 5 foot tall male student stands so that the tip of his shadow coincides with the tip of the flag pole’s shadow. • a. Are the two triangles similar? Explain. AA ~ Yes,
11. In order to estimate the height, h, of a flag pole, a 5 foot tall male student stands so that the tip of his shadow coincides with the tip of the flag pole’s shadow. h 5 • b. Find the height, h, of the flag pole. 6 1 18 3 6h = 90 x = 15ft x = 15ft
HW Problem FRONT PAGE # 11 12 n 27.5 P = 34 P = 85 2x = 55 2n = 15 5y = 60 n = 7.5 x = 27.5 y = 12