Using Proportions to Solve Geometry ProblemsSection 6.3

Scale Factor• Two polygons are similar polygons if corresponding angles are

congruent and corresponding side lengths are proportional.

• The scale or scale factor is the ratio that describes how the dimensions of the two figures are related.

• List all pairs of congruent angles.

• Check that the ratios of corresponding side lengths are equal.

• What is the scale factor?

Perimeters of Similar Polygons• If two polygons are similar, then the ratio of their perimeters is

equal to the ratio of their corresponding side lengths.

Perimeters of Similar Figures

Sections 6.4 & 6.5

Similarity Postulates

Angle-Angle Similarity Postulate (AA)If two angles of one triangle are congruent

to two angles of another triangle, then the two triangles are similar.

Side-Side-Side Similarity TheoremIf the corresponding side lengths of two

triangles are proportional, then the triangles are similar.

Side-Angle-Side Similarity TheoremIf an angle of one triangle is congruent to

an angle of a second triangle and the lengths of the sides including these angles are proportional, then the triangles are similar.

Show that each set of triangles is similar

Show that the two triangles are similar.

PRACTICEPractice WS