Answer: In a regular decagon, there are 10 lines of symmetry.
Explanation:
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 will look unchanged.
A regular decagon has 10 vertices and 10 edges.
To draw line of symmetry :
1.Draw lines to meet the exactly opposite point [shown by red color in the picture attached with the answer].
∴ 10 vertices will form 5 lines of symmetry.
2.Draw lines from the mid points of all the edges to the midpoint of the exactly opposite edge [shown by blue color in the picture attached with the answer].
∴ 10 edges will form 5 lines of symmetry.
⇒Total lines of symmetry in a decagon =5+5= 10