- #1

- 676

- 46

I know that e

^{ix}e

^{-ix}= 1 but if I write the product of the 2 exponentials as infinite series I get

Σ

_{n}Σ

_{m}x

^{n}/(n!) (-x)

^{m}/(m!)

without knowing the result is 1 using exponentials how would I get the result of this product of 2 infinite sums ?

Thanks