(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) .