# Delta Cauchy-Schwarz inequality

Let $a,b \in \mathbb{T}$. For rd-continuous $f,g \colon [a,b]\cap \mathbb{T} \rightarrow \mathbb{R}$ we have $$\displaystyle\int_a^b |f(t)g(t)| \Delta t \leq \sqrt{\left( \displaystyle\int_a^b |f(t)|^2 \Delta t \right) \left( \displaystyle\int_a^b |g(t)|^2 \Delta t \right)}$$