SS 4.2 Ratios within Similar Triangles 1) Teaching Target: I can use equivalent ratios to compare corresponding sides of similar triangles. 2) Homework: Inv 3-4 pkt p. 14 – Termite Puzzle 3) Warm-Up: If the scale factor is 1.5 what are the side lengths of the image? (pay close attention to the figures!)

pkt p. 13 Which triangles are similar? A B C D For each triangle, find the ratio of the shortest side to the longest side, and the ratio of the shortest side to the middle side.

A B C D 13 Short to Long Short to Mid C, D none A, DA, D A, CA, C

Short to Long Short to Mid C D A, DA, D A, CA, C D A C, D

A B C D A, DA, D A, CA, C none 2. What do you notice about the ratios for the similar triangles? Similar triangles have the SAME ratio! 3. What do you notice about the ratios for the non-similar triangles? Non-similar triangles have different ratios!

Choose two similar triangles. Find the scale factor from the smaller triangle to the larger triangle. What information does the scale factor give? A to C = A B C D A, DA, D A, CA, C C, D none A to D = C to D = D to A = 0.4 D to C = 0.6

5. Compare the information given by the ratios of the side lengths and the information given by the scale factor. Name three things this information gives. Similar figures have a constant scale factor and their ratios of corresponding side lengths will be equivalent. The scale factor gives the amount of stretching (or shrinking) from the original figure to the image. The ratio of adjacent side lengths within a figure gives an indication of the shape of the original figure (and image), since it compares measures within one figure.

SS 4.2 Ratios within Similar Triangles Did I Reach my Learning Target? Can I use equivalent ratios and scale factor to compare corresponding sides of similar triangles. Homework: Inv 3-4 pkt p. 14 – Termite Puzzle