Stretching and Shrinking Students will be able to use scale factor to determine distances, students will be able to find unknown heights using similar figures.
Investigation 4: Similarity and Ratios
Homework Investigation 4 Page 90 A 1,3,4-7, 12,14,16,18 B 16,18,40,42,43,
Warm Up
4.1 Ratio within Similar Parallelograms What information does the ratio of adjacent side lengths within a rectangle give you?
Terms Ratios comparison of two quantities, such as 2 lengths Equivalent Ratio’s like equivalent fractions, simplify down to the same value Proportion an equation setting two ratios equal
Problem 4.1 page 82 Watch video A,B,C Adjacent sides Sides that share a vertex or corner
Warm Up
4.2 Ratios within similar Triangles For a pair of triangles, if the measure of corresponding angles are equal, how can you use ratios of side lengths to determine whether or not the triangles are similar?
Problem 4.2 pg 85 When setting up ratios make sure you are comparing corresponding sides, short to short and long to long Pg 84 Who is correct? Prob 4.2 A,B,C,D
Warm Up
4.3 Finding Missing parts If two shapes are similar, how can you use information about the shapes to find unknown side lengths, perimeters and areas?
Prob 4.3 pg 86 2 methods Scale factor from one figure to the other Use ratios of the side lengths within each figure A,B,C,D
Warm Up
4.4 Using Shadows to find height How can you use similar triangles to estimate the heights of tall objects?
Problem 4.4 pg 88 Watch Video Answer questions on page 88 Discuss the shadow method Lab to measure objects
Essential questions What information does the ratio of adjacent side lengths within a rectangle give you? For a pair of triangles, if the measure of corresponding angles are equal, how can you use ratios of side lengths to determine whether or not the triangles are similar? If two shapes are similar, how can you use information about the shapes to find unknown side lengths, perimeters and areas? How can you use similar triangles to estimate the heights of tall objects?