Answer:
Number of sides of a regular polygon whose smallest angle of rotation is [tex]18^{\circ}[/tex] is 20. so correct option is 20.
Solution:
Need to determine sides of a regular polygon having smallest angle of rotation as [tex]18^{\circ}[/tex]
In above case smallest angle of rotation is same as central angle of regular polygon.
So now we need to determine number of sides of regular polygon whose central angle is [tex]18^{\circ}[/tex]
Number of sides of regular polygon [tex]= \frac{360}{\text {central angle}}[/tex]
So for a regular polygon having central angle = [tex]18^{\circ}[/tex]
Number of sides = [tex]\frac{360}{18} = 20[/tex]
Hence number of sides of a regular polygon whose smallest angle of rotation is [tex]18^{\circ}[/tex] is 20.