Question

b) How many diagonals are there in a regular polygon of 10 sides​

Answer 1

Answer:

How many diagonals of a regular decagon (a 10 sided polygon) are not parallel to any of the sides (AMC12)? A decagon has (10 2) – 10 = 35 diagonals. Each pair of opposing sides has three diagonals which are parallel to them, so 5*3 = 15 of the diagonals are parallel to a side.

Answer 2

Answer:

Decagon (10 sides):

n(n-3)/2 = 10(10-3)/2

= 10*7/2

= 70/2

= 35 diagonals.

hope it helps.....