Problem 3 Identifying Symmetry in a Three-Dimensional Object

Symmetric Design Does the object have reflectional symmetry in a plane, rotational symmetry about a line, or both?

1. 

   The bowl has both reflectional symmetry in a plane and rotational symmetry about a line.

2. 

   The pitcher has reflectional symmetry in a plane.

✓ Got It?

3. Does the lampshade have reflectional symmetry in a plane, rotational symmetry about a line, or both?

   

✓ Lesson Check

Do you know HOW?

Use the figure below for Exercises 1 and 2.

1. Does the figure have line symmetry? If so, copy the figure and draw its line(s) of symmetry.

   

2. Does the figure have rotational symmetry? If so, what is the angle of rotation?

3. What type(s) of symmetry does the three-dimensional figure have?

   

Do you UNDERSTAND?

4. Vocabulary If a figure has point symmetry, must it also have rotational symmetry? Explain.

5. Error Analysis Your friend thinks that the regular pentagon in the diagram below has 10 lines of symmetry. Explain and correct your friend's error.

   

6. Open-Ended The word CHECKBOOK has a horizontal line of symmetry. Find two other words for which this is true.