# Math Help - Parseval Relation

1. ## Parseval Relation

Derive from $\sum_{k} \vert \vert ^2 = \|x\|^2$
the following formula which is called the parseval relation:

$ = \sum_k \overline{}.$

2. Use the formula $\langle x,y\rangle=\frac{1}{4}\left(||x+y||^2-||x-y||^2\right)-\frac{{\rm i}}{4}\left(||x+{\rm i}y||^2-||x-{\rm i}y||^2\right)$.

3. thank you for the hint! I'll see if I can use it to find the solution to get from A to B
If I get stuck I'll let you know.