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Applications of Similar Triangles. Definition of similarity Solving for unknowns Application problems. Two triangles are considered to be similar if and only if:. they have the same shape. corresponding angles are equal.
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Applications of Similar Triangles • Definition of similarity • Solving for unknowns • Application problems
Two triangles are considered to be similar if and only if: • they have the same shape • corresponding angles are equal • the ratio of the corresponding side lengths are equal
F C x 1 m A B D E 72 cm 18.5 m Ex #1: To estimate the height of a tree, Margaret held a metre stick perpendicular to the ground and observed the length of its shadow was 72 cm. Then she measured the length of the tree’s shadow as 18.5 m. What was the approximate height of the tree? Step 1: Draw a labeled diagram. Step 2: Identify two similar triangles. ABC ~ DEF Step 3: Write equivalent ratios
F C x 1 m A B D E 72 cm 18.5 m Step 4: Use the ratios that apply to solve for x. 0.72x = 18.5 x = 25.7 m
Ex #2: Surveyors have laid out triangles to find the length of a lake. Calculate this length, AB. ft Step 1: Draw a labeled diagram. PROVIDED ft Step 2: Identify two similar triangles. ft ACB ~ ECD Step 3: Write equivalent ratios
D F C Ex #3: On a camping expedition, two campers decide to calculate the length of the small lake just beside their campsite. They mark off a 2 m line parallel to the shore of the lake. Then, they step back from the line until they can site each end of the lake with one end of the line they have marked. From this position, they can measure the distance to one end of the 2 m line [3.1 m]. The distance to the corresponding end of the lake is indicated on a bike trail sign [1200 m]. How long is the lake? Step 1: Draw a labeled diagram. PROVIDED Step 2: Identify two similar triangles. ABC ~ DFC
D F C Step 3: Write equivalent ratios In ABC ~ DFC, Step 4: Use the ratios that apply to solve for x. 3.1(AB) = 2400 x = 774.19 m