8-9 Congruent Polygons

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8-9 Congruent Polygons

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8-9 Congruent Polygons

Problem of the Day

The sum of two decimals is 9.3; their difference is 4.3, and their product is 17.00. What are they?2.5, 6.8

8-9 Congruent Polygons

Learn to identify congruent figures and to use congruence to solve problems.

8-9 Congruent Polygons

Vocabulary

congruent figures

8-9 Congruent Polygons

You know that angles that have the same measure are congruent.

Congruent figures have the same shape and same size. This means the corresponding sides and corresponding angles are congruent.

8-9 Congruent Polygons

Additional Example 1A: Identifying Congruent Figures

These figures do not have the same shape and they are not the same size.

These figures are not congruent.

Decide whether the figures in each pair are congruent. If not, explain.

8-9 Congruent Polygons

Additional Example 1B: Identifying Congruent Figures

Decide whether the figures in each pair are congruent. If not, explain.

These figures have the same shape and size.

These figures are congruent.

8-9 Congruent Polygons

Check It Out: Example 1A

Decide whether the figures in each pair are congruent. If not, explain.

Each figure is a trapezoid. The corresponding sides are 5.7 in., 7.5 in., 5 in., and 10 in.

These figures are congruent.

8-9 Congruent Polygons

Check It Out: Example 1D

Decide whether the figures in each pair are congruent. If not, explain.

Each figure is a rectangle. Each short side of each rectangle measures 4 cm. Each long side of each rectangle measures 9 cm.

These figures are congruent.

8-9 Congruent Polygons

Additional Example 2: Consumer Application Jodi needs a sleeping pad that is congruent to her sleeping bag. Which pad should she buy?

Both sleeping pads are trapezoids. Only sleeping pad B is the same size as the sleeping bag.

Sleeping pad B is congruent to the sleeping bag.

8-9 Congruent Polygons

Check It Out: Example 2

Tomi needs a frame that is congruent to her flag. Which frame should she buy?

Both frames are triangles. Only Frame B is the same size as the flag.

Frame B is congruent to the flag.

11.2 in.

7.8 in.

4 in.10 in. 11.2 in.

7.8 in.9.2 in.

4 in.4 in.

Flag Frame A Frame B

8-9 Congruent Polygons

Standard Lesson Quiz

Lesson Quizzes

Lesson Quiz for Student Response Systems

8-9 Congruent Polygons

Lesson QuizTrue or false?

1. If two figures have sides of the same length, they are congruent.

2. Congruent figures have angle measures that are equal.

3. Decide whether the figures are congruent. If not, explain.

true

false

No; both are quadrilaterals but they are not the same size or shape.

8-9 Congruent Polygons

1. Which of the following statements is false?

A. If two figures have the same shape, then they are congruent. B. Congruent figures have angle measures that are equal. C. Congruent figures have equal side lengths. D. none

Lesson Quiz for Student Response Systems

octagon, not regular octagon, not regular

8-9 Congruent Polygons

2. Which of the following statements is true?

A. If two figures have the same angle measures, then they are congruent. B. If two figures have the same side lengths, then they are congruent. C. If two figures have the same shape and size, then they are congruent. D. none

Lesson Quiz for Student Response Systems

8-9 Congruent Polygons

3. Decide whether the figures are congruent. If not, explain.

A. No; both are trapezoids, but they are not the same size. B. No; both are trapezoids, but they are not the same shape. C. No; both are not trapezoids. D. Yes

Lesson Quiz for Student Response Systems