\(L=\int_a^b\sqrt{f'\left(t\right)+g'\left(t\right)+h'\left(t\right)}dt\)
\(n=\frac{N\sigma^2}{abc}\)
\(P=\int_R^{ }f\left(x,y\right)\ dA=\int_{\alpha}^{\beta}\int_a^bf\left(r\ \cos\ \theta,\ \sin\ \theta\right)r\ dr\ d\theta\)
\(\int_0^8\frac{\left(x+2\right)dx}{x^2-2x-3}\)
\(m=\frac{y_2-y_1}{x_2-x_1}=\frac{\Delta y}{\Delta x}=\frac{dy}{dx}\)