x^n+x^(n-1)…………x+1在複數域和實數域上因式分解

x^n+x^(n-1)…………x+1在複數域和實數域上因式分解

在複數域上:x^n+x^(n-1)…………x+1=(x-(cos(2π/(n+1))+isin(2π/(n+1)))(x-(cos(4π/(n+1))+isin(4π/(n+1)))……(x-(cos(2nπ/(n+1))+isin(2nπ/(n+1)))
在實數域上:當n為奇數時,x^n+x^(n-1)…………x+1=(x+1)(x²;-2cos(2π/(n+1))+1)(x²;-2cos(4π/(n+1))+1)……(x²;-2cos((n-1)π/(n+1))+1)
當n為偶數時,x^n+x^(n-1)…………x+1=(x²;-2cos(2π/(n+1))+1)(x²;-2cos(4π/(n+1))+1)……(x²;-2cos(nπ/(n+1))+1)