Parseval's equation

Parseval's equation

[′pär·sə·vəlz i‚kwā·zhən]
(mathematics)
The equation which states that the square of the length of a vector in an inner product space is equal to the sum of the squares of the inner products of the vector with each member of a complete orthonormal base for the space. Also known as Parseval's identity; Parseval's relation.