(1 point) The area A of the region S that lies under the graph of the continuous function f on the interval a, b is the limitof the sum of the areas of approximating rectangles. A=\lim _{n \rightarrow \infty}\left[f\left(x_{1}\right) \Delta x+f\left(x_{2}\right) \Delta x+\ldots+f\left(x_{n}\right) \Delta x\right]=\lim _{n \rightarrow \infty} \sum_{i=1}^{n} f\left(x_{i}\right) \Delta x \text { where } \Delta x=\frac{b-a}{n} \text { and } x_{i}=a+i \Delta x \text { Use this definition to find an expression for the area } A \text { under the graph of the function } f(x)=\frac{2 x}{x^{2}+1} \text { on the interval }[1,4] \text {. } A=\lim _{n \rightarrow \infty} \sum_{i=1}^{n}