The definite integral 
( )
b
∫a f x dx
 is the area bounded by the curve y = f (x), the
ordinates x = a, x = b and the x-axis To evaluate this area, consider the region PRSQP
between this curve, x-axis and the ordinates x = a and x = b (Fig 7 2) Divide the interval [a, b] into n equal subintervals denoted by [x0, x1], [x1, x2] ,