Orthogonality

Definition

Function

$f$ and $g$ are orthogonal if ${\int }_a^{b}f(x)g(x)dx=⟨f,g⟩$

Vector

$⟨\mathbf{v},\mathbf{w}⟩=0\Rightarrow \mathbf{v}\perp \mathbf{w}$

The two vectors are orthogonal if their Inner product is 0.