n(n-3)/2 n - number of sides
...or an easy way for thickos that dont understand algebra forumals : n-3 x n / 2
Chat with our AI personalities
It is: 0.5*(10 squared - (3*10)) = 35 diagonals
decagon
35
A decagon has 10 sides and 35 diagonals
A decagon has 35 diagonals. This can be computed by multiplying ten by seven and dividing by two. Seven is derived from the number of sides minus three.