Categories Mathematics (n+1)n(n-1)/3.2.1 = Post author By esimpk Post date June 16, 2021 (n+1)ι 3ι(n-2)ι/(n+1)ι (n+1)ι/3ι(n-2)ι (n-2)ι ← (cos(x)-cos3x)/(sin3x-sin(x)) = → (n+2)(n+1)n =