Hence, by chain rule
df
dx  =
cos
2
dv
dt
t
x
dt
⋅dx
=
⋅
It is normal practice to express the final result only in terms of x Thus
df
dx  =
2
cos
2
2 cos
t
x
x
x
⋅
=
EXERCISE 5 2
Differentiate the functions with respect to x in Exercises 1 to 8 1