[size=100]If [math]f[/math] is continuous on an interval [math]\left[a,b\right][/math], and the function [math]F\left(x\right)[/math] is defined by[br][math]F\left(x\right)=\int_a^xf\left(t\right)dt[/math], then [math]F'\left(x\right)=f\left(x\right)[/math] on [math]\left(a,b\right)[/math].[/size]