The purpose of this lab is to use Maple to introduce you to Taylor polynomial approximations to functions, including some applications.

You should check for yourself that the cubic polynomial satisfying these four conditions is

The general form of the Taylor polynomial approximation of order to is given by the following

which you should recognize as a power series that has been truncated.

over the interval .

>with(CalcP7);

The exponential function can be approximated at a base point zero with a polynomial of order four using the following command.

>Taylor(exp(x),x=0,4);You might want to experiment with changing the order. To see and its fourth order polynomial use

>TayPlot(exp(x),x=0,{4},x=-4..4);This plots the exponantial and three approximating polynomials.

>TayPlot(exp(x),x=0,{2,3,4},x=-2..2);Notice that the further away from the base point, the further the polynomial diverges from the function. the amount the polynomial diverges i.e. its error, is simply the difference of the function and the polynomial.

>plot(abs(exp(x)-Taylor(exp(x),x=0,3)),x=-2..2);This plot shows that in the domain x from -2 to 2 the error around the base point is zero and the error is its greatest at x = 2 with a difference of over one. You can experiment with the polynomial orders to change the accuracy. If your work requires an error of no more than 0.2 within a given distance of the base point then you can plot your accuracy line y = 0.2 along with the difference of the function and the Taylor approximation polynomial.

>plot([0.2,abs(exp(x)-Taylor(exp(x),x=0,3))],x=-2..2,y=0..0.25);We knew this would have some of its error well above 0.2. Change the order from three to four. As you can see there are still some values in the domain close to x = 2 whose error is above 0.2. Now try an order of 5. Is the error entirely under 0.2 between x = -2 and x = 2? Larger orders will work as well but order five is the minimum order that will keep the error under 0.2 within the given domain.

- For the following functions and base points, determine what
minimum order is required so that the Taylor polynomial approximates the
function to within a tolerance of over the given
interval.
- a)
- , base point , interval .
- b)
- , base point , interval .
- c)
- , base point , interval .
- d)
- ,base point , interval .

- You read in the begining of the background that a Taylor Polynomial must have the same y-value, at the base point, as the original function. Also, the derivatives at that point must be the same. Three functions and three second-order polynomials are given; determine which function goes with which Taylor Polynomial by following the steps below.

- a)
- Enter the functions and the polynomials.
- b)
- Find the y-values of all six at .
- c)
- Find the first derivative at 0 of all six.
- d)
- Find the second derivative at 0 of all six.
- e)
- Which Taylor Polynomials go with which functions.

2006-09-21