A Level Maths Notes: FP2 – Inequalities Involving Integrals and Series
We can estimate the value of the sum of a series of
terms
by
representing the sum by a sequence of rectangles of base 1 and
height
for
This
can also be estimated using the integral![]()
Then
The
integral is an underestimate for the sum of the series since since
-
we can add a sequence of these expressions to get
![]()
Similarly We can estimate the value of the sum of the
series
by
representing the sum by a sequence of rectangles of base 1 and
height
for
This
can also be estimated using the integral![]()
Then
The
integral is an overestimate for the sum of the series since since
-
we can add a sequence of these expressions to get
![]()
Hence
![]()
In general if
for
then
![]()
and if
for
then
![]()