We say
that sin x is an anti derivative (or an integral) of cos x Similarly, in (2) and (3), 
3
3
x  and
ex are the anti derivatives (or integrals) of x2 and ex, respectively Again, we note that
for any real number C, treated as constant function, its derivative is zero and hence, we
can write (1), (2) and (3) as follows :
(sin
+ C)
=cos
d
x
x
dx
, 
3
2
(
+ C)
3
=
d
x
x
dx
and 
(
x+ C) =
x
d
e
e
dx
Thus, anti derivatives (or integrals) of the above cited functions are not unique Actually, there exist infinitely many anti derivatives of each of these functions which
can be obtained by choosing C arbitrarily from the set of real numbers