6.3 Use Similar Polygons Learning Target: Students will be able to use proportions to identify similar polygons. March 31, 2014

Ex 1: Use Similarity Statements Similar Polygons- two polygons are similar if corresponding angles are congruent and corresponding side lengths are proportional In the diagram ΔABC ~ ΔDEF a)List all pairs of congruent angles. b)Check that the ratios of corresponding side lengths are equal. c)Write the ratios of the corresponding side lengths in a statement of proportionality. A F E D C B

Ex 2: Find the Scale Factor Scale Factor- the ratio of the lengths of two corresponding sides of two polygons Determine whether the polygons are similar. If they are, write a similarity statement and find the scale factor of RSTU and DEFG F E G D U T S R 3 : 2 RSTU ~ DEFG

Ex 3: Use Similar Polygons In the diagram, ΔABC ~ ΔGHJ. Find the value of x J H G x C B A

Ex 4: Find Perimeters of Similar Figures Theorem 6.1- Perimeters of Similar Polygons If two polygons are similar, then the ratio of their perimeters is equal to the ratios of their corresponding side lengths. You are constructing a rectangular play area. A playground is rectangular with length 25 meters and width 15 meters. The new play area will be similar in shape, but only 10 meters in length. a) Find the scale factor of the new play area to the playground. 10 : 25 or 2 : 5 b) Find the perimeter of the playground and the play area. Playground = 80 meters Play Area -

Ex 5: Use a Scale Factor In the diagram, ΔMNP ~ ΔRST. Find the length of the altitude NL. Find the scale. Find NL. R 2014 S 18 L T P 27 N 30 M

Guided Practice In the diagram, ΔJKL ~ ΔEFG Find scale factor. Find KM F E H G M 48 L K J

Assignment Pg. 376 #4-24 even