Lesson 5-2 Similar Polygons

Similar Polygons Definition: Two polygons are similar if: 1. Corresponding angles are congruent. 2. Corresponding sides are in proportion. Two polygons are similar if they have the same shape not necessarily have the same size. The scale factor is the ratio between a pair of corresponding sides. Scale Factor: Type notes here

Naming Similar Polygons When naming similar polygons, the vertices (angles, sides) must be named in the corresponding order. P Q A B D C S R

The two polygons are similar. Solve for x, y and z. 5 z x 10 y 15 30 20 B C A D F G E H Example- The two polygons are similar. Solve for x, y and z. Step1: Write the proportion of the sides. Step 2: Replace the proportion with values. Step 3: Find the scale factor between the two polygons. Note: The scale factor has the larger quadrilateral in the numerator and the smaller quadrilateral in the denominator. Type notes here Step 4: Write separate proportions for each missing side and solve.

½ Example: If ABC ~ ZYX, find the scale factor from ABC to ZYX. Scale factor is same as the ratio of the sides. Always put the first polygon mentioned in the numerator. 7 9 5 18 10 14 C A B Z Y X The scale factor from ABC to ZYX is 2/1. ½ What is the scale factor from ZYX to ABC?

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