Derivative of f at c is denoted by f ′(c) or 
( ( )) |c
d
dxf x The
function defined by
0
(
)
( )
( )
lim
h
f x
h
f x
f
x
h
→
+
−
′
=
wherever the limit exists is defined to be the derivative of f The derivative of f is
denoted by f ′(x) or 
d( ( ))
dxf x
or if y = f (x) by dy
dx or y′ The process of finding
derivative of a function is called differentiation