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Learn to identify, draw, and explain similar polygons using scale factors. Discover how corresponding angles and side lengths are key properties in determining similarity. Includes examples and practice problems.
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Chapter 4 – Scale Factors and Similarity Key Terms • Polygon – a two-dimensional closed figure made of three or more line segments
4.4 Similar Polygons Learning Outcome: To be able to identify, draw, and explain similar polygons and solve problems using the properties of similar polygons
Similar Polygons • Similar polygons which have been multiplied by a scale factor show an enlargement or reduction. Therefore, similar polygons have: • Corresponding Angles - Equal internal angles • Corresponding Side Lengths - Proportional side lengths (because of scale factor) • But unlike Similar Triangles BOTH need to be true for the polygons to be similar.
Example 1: Identify Similar Polygons The two quadrilaterals look similar. Is LOVE a true enlargement of MATH? Explain. 4.2 3 L M H E 1.1 1.5 1.54 2.1 A O 3.5 T 4.9 V
Example 1: Identify Similar Polygons 4.2 3 L M H E 1.1 1.5 1.54 2.1 A O 3.5 T 4.9 V Compare corresponding sides: Compare corresponding angles: Note: The sum of the interior angles in a quadrilateral is 360 The corresponding angles are equal and the corresponding side lengths are proportional with a scale factor of 1.4. Therefore LOVE is a true enlargement of MATH by a scale factor of 1.4.
Example 2: Determine a Missing Side Length K J Q P 5cm R 9cm S 32cm L M
Example 2: Determine a Missing Side Length K J Q P 5cm R 9cm S 32cm Since the rectangles are similar; the side lengths are proportional. Use corresponding sides to set up a proportion. L M The missing side length is 57.6cm.
Show you Know – The two trapezoids shown are similar. Determine the missing side length. Show your work
Assignment • Page 157 (1, 3, 5-6, 9, 11)