**Hello!**

Use this "formula":

\(\displaystyle \int\limits_a^b \approx \frac{b-a}{n}[\frac{f(x_0)+f(x_n)}{2}+f(x_1)+f(x_2)+\dots+f(x_{n-1})]\)

Your \(\displaystyle h\) is \(\displaystyle \frac{b-a}{n}\).

This can be easily proved if you take your section \(\displaystyle /[a,b]\) and dividing him to \(\displaystyle n\) equal parts, and then taking the trapezes to evaluate the integral.