Thus, the region AOBA may be stated as
the region bounded by the curve y = x 2, y = 4
and the ordinates x = –2 and x = 2 Therefore, the area of the region AOBA
= 
2
2 ydx
−∫
  [ y = (y-coordinate of Q) – (y-coordinate of P) = 4 – x 2]
= 
(
)
2
2
20
4
x
dx
−
∫
(Why )
=
2
3
0
2 4
x3
x

−




 
8
2 4 2
3


=
× −



32
3
=
Remark From the above examples, it is inferred that we can consider either vertical
strips or horizontal strips for calculating the area of the region Henceforth, we shall
consider either of these two, most preferably vertical strips