Preliminary Remarks and examples:
If a function is
times continuously differentiable at a point
compute its Taylor polynomial of degree at as follows:
where
a remainder term which satisfies
with
we can
the maximum value of
is
for all such
that
.
The Taylor polynomial is an approximation of the function; the remainder term
measures the error in this approximation. For example, the Taylor polynomial
of degree
at
for the function
is computed as follows:
Putting these terms together we
get
The class software can do the entire computation for us, by
using Compute+Power Series and choosing 5 for the number of terms
and
for the power.
The term
represents the remainder, and signifies that the remainder is
a fifth order term.
In the figure below both
and its 4th degree Taylor polynomial about zero
are plotted. (When you do this you should make sure that you do not include
the
term in the plot.)
We see that close to 0 the two curves are identical, further away they no
longer match. If we want a better measure of the actual error we plot We see that in the interval
The Taylor series of at is
the Maclaurin series of .
Problems
1.
a.
this error is less than 0.05.
. The special case of
is called
i.Use the class software to find the Taylor polynomials up to degree
6 for
centered at
. Graph
polynomials on a common screen.
ii.Evaluate
and these polynomials at
and these
and
.
iii.Comment on how the Taylor polynomials converge to
b.
.
i.Use the class software to find the Taylor polynomials up to degree
3 for
centered at
on a common screen.
ii.Evaluate
. Graph
and these polynomials at
and these polynomials
and
.
iii.Comment on how the Taylor polynomials converge to
.
More Problems
Use the class software to find the Taylor polynomial of degree 7 for the given
functions around the indicated points. Plot the function together with the Taylor
polynomial in a single graph. Then plot the actual error:
your units carefully and estimate the size of the error.
. Choose
c.
d.
e.
f.
Would the Taylor polynomials of degree 5 be better or worse
approximations to the functions? Explain. What about the degree 9 Taylor
polynomials? Explain.
g.
Find the Maclaurin series for
which is equal to .
. Then use it to find a series