Answer:- In a regular decagon, there are 10 reflectional symmetries.
Reflectional symmetry or Line of symmetry divides a figure into two equal halves so that if you flip the half image over the line of symmetry, the figure would look same.
A regular decagon has 10 vertices and 10 edges.
where 10 vertices forms 5 lines of symmetry.
and 10 edges forms 5 lines of symmetry.
⇒Total lines of symmetry in a decagon =5+5= 10
Thus, In a regular decagon, there are 10 reflectional symmetries.