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7.2-7.3 Similar polygons & proving triangles similar. Boyd/Usilton. Similar polygons. Two polygons are similar if corresponding angles are congruent and if the lengths of corresponding sides are proportional. (see board for figure)
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7.2-7.3 Similar polygons & proving triangles similar Boyd/Usilton
Similar polygons • Two polygons are similar if corresponding angles are congruent and if the lengths of corresponding sides are proportional. (see board for figure) • When three or more ratios are equal, you can write an extended proportion.
Scale factor • The ratio of corresponding linear measurements of two similar figures. • Find the ratio of the lengths of corresponding sides. Scale factor of ABC to XYZ is 5:2.
Postulate 7-1 Angle-Angle Similarity (AA ~) Postulate • If two angles of one triangle are congruent to two angles of another triangle, then the triangles are similar. If... <S = <M and <R = <L Then… SRT ~ MLP
Theorem 7-1 Side-angle-side (SAS ~) Theorem • If an angle of one triangle is congruent to an angle of a second triangle, and the sides that include the two angles are proportional, then the triangles are similar. • If… AB = AC and QR QS <A = <Q Then…. ABC ~ QRS
Theorem 7-2 Side-side-side (SSS~) Theorem • If the corresponding sides of two triangles are proportional, then the triangles are similar. If…. AB = AC = BC QR QS RS Then… ABC ~ QRS