2.0 Geometrical Meaning

$\int\limits_a^b {f\left( x \right)dx} $ is defined as the area bounded by $f\left( x \right)$, $x = a$, $x = b$ and $x$-axis.

We call a Area function $A\left( x \right)$ whose value is given by $A\left( x \right) = \int\limits_a^x {f\left( x \right)dx} $