1  Area function
We have defined 
( )
b
∫a f x dx
 as the area of
the region bounded by the curve y = f(x),
the ordinates x = a and x = b and x-axis Let x
be a given point in [a, b] Then 
( )
x
a f x dx
∫
represents the area of the light shaded region
Fig 7 3
INTEGRALS         335
in Fig 7