La f , g : [ a , b ] → R {\textstyle f,g:[a,b]\to \mathbb {R} } være kontinuerlige, og g ≥ 0. {\displaystyle g\geq 0.} Da finnes det x ^ ∈ [ a , b ] {\displaystyle {\widehat {x}}\in [a,b]} slik at ∫ a b f ( x ) g ( x ) d x = f ( x ^ ) ⋅ ∫ a b g ( x ) d x . {\displaystyle \int _{a}^{b}f(x)g(x)\mathop {dx} =f({\widehat {x}})\cdot \int _{a}^{b}g(x)\mathop {dx} .} Hvis g = 1 {\displaystyle g=1} : ∫ a b f ( x ) d x = f ( x ^ ) ⋅ ( b − a ) . {\displaystyle \int _{a}^{b}f(x)\mathop {dx} =f({\widehat {x}})\cdot (b-a).}