Chapter 12.6, Problem 17E

To determine

To find:the tray have rotational symmetry or not, and the degree of rotation to play a CD in position 3 when CD 1 is playing.

Answer to Problem 17E

1. The tray has rotational symmetry.
2. We have to rotate ${144}^{\circ }$ tray to play CD 3 when CD 1 is playing.

Explanation of Solution

Given : the figureprovided in the question,

Calculation :

1. The tray has rotational symmetry because when we rotate it ${360}^{\circ }$, it will coincide itself.
2. To play the CD in position 3 tray must be rotate ${144}^{\circ }$ because to change one position to another position it is required to rotate the tray ${72}^{\circ }$ .

Hence,

1. The tray has rotational symmetry.
2. We have to rotate ${144}^{\circ }$ tray to play CD 3 when CD 1 is playing