(a)
\Consider the function as
.
Differentiate on each side with respect to
.

Therefore,
for
.
Hence the function
is increasing for
.
Thus,
for
.
if
.
(b)
\Consider
for
.
Replace
in above expression.
is also true for
.
Comparison property of integrals :
\If
for
, then
.


(a)
if
.
(b)
.