The delta function is defined as follows:
If m = n {\displaystyle m=n}
δ m , n = 1 {\displaystyle \delta _{m,n}=1}
Else if m ≠ n {\displaystyle m\neq n}
δ m , n = 0 E x a m p l e : ( T h e d e l t a f u n c t i o n i s n o n − z e r o o n l y w h e n < m a t h > m = n {\displaystyle \delta _{m,n}=0Example:(Thedeltafunctionisnon-zeroonlywhen<math>m=n} . So, α m {\displaystyle \alpha _{m}} is non-zero only when m = n {\displaystyle m=n} . We may then conclude what is stated below.)
δ m , n α m = α n {\displaystyle \delta _{m,n}\alpha _{m}=\alpha _{n}}
. So, 
is non-zero only when . We may then conclude what is stated below.)
