The Taylor Formula

Содержание

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The Taylor Formula where For instance, where

The Taylor Formula

where

For instance,

where

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Question 1. If Solution: Taylor’s formula tells us for all real numbers x, then

Question 1. If

Solution: Taylor’s formula tells us

for all real numbers

x, then
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Therefore

Therefore

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Answers to Questions from Light #7: Taylor’s Formula & Infinite Series

Answers to Questions from Light #7:
Taylor’s Formula & Infinite Series

Question

2:

Question 4:

Question 3:

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Calculus++ Infinite Series

Calculus++

Infinite Series

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Question 1. What is the greatest value of b for which

Question 1. What is the greatest value of b for which

any function f that satisfies the properties (i), (ii), and (iii) must also satisfy f (1) < 5?
(i) f (x) is infinitely differentiable for all x;
(ii) f (0) = 1, and
(iii) for all

Solution: Taylor’s formula tells us

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Using the properties (ii) and (iii) we obtain Solve the equation

Using the properties (ii) and (iii) we obtain

Solve the equation to

obtain b = 12.

Therefore, the greatest value of b for which f (1) < 5 is 12.

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In particular, where That is

In particular,

where

That is

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Question 2. Use the Taylor formula to show that e is

Question 2. Use the Taylor formula to show that e is

irrational.

Solution. Let us assume that e is rational,

Then the Taylor formula tells us that for any n:

Take

and multiply both sides

of the double inequality by n! to obtain

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an integer number Contradiction! Thus, our assumption that e is a

an integer number

Contradiction!

Thus, our assumption that e is a rational number

leads to a contradiction.
Therefore, e is an irrational number.

Therefore

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Question 3. Find Solution. The Taylor formula tells us that for

Question 3. Find

Solution. The Taylor formula tells us that for any

n:

Therefore

where is a number between 0 and 1.
Multiply by to obtain

= M, an integer number

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Since sin x is equivalent to x, when x is small, we obtain Hence,

Since sin x is equivalent to x, when x is small,

we obtain

Hence,

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Consider an infinite sequence If we add all the terms of

Consider an infinite sequence

If we add all the terms of this

sequence we obtain an infinite series

For example, consider the sequence

The corresponding infinite series is

What is the value of this infinite series?
This infinite series does not have a value.

or ?!

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The sum of the first n terms of an infinite series,

The sum of the first n terms of an infinite series,

Sn, is called the n-th partial sum of the series

An infinite series converges, if converges the sequence of its partial sums:

The limit, S, of the sequence of partial sums is the sum of the infinite series.

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If |b| Example. The geometric series The n-th partial sum of

If |b| < 1, the sequence Sn converges.

Example. The geometric series


The n-th partial sum of the geometric series is given by

If and |b| > 1, the sequence of partial sums Sn diverges.

If a = 0, the sequence Sn converges to 0.

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If b = 1, the sequence of partial sums Sn diverges

If b = 1, the sequence of partial sums Sn diverges

(unless a = 0).

If b = –1, the sequence of partial sums Sn also diverges (again, unless a = 0).

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A necessary condition for convergence. If a series converges, then Indeed,

A necessary condition for convergence.

If a series

converges, then

Indeed, if the sequence

of partial sums

converges, then (Cauchy criterion)

and

Set m = 1, then

Therefore

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Question 5. Which of the following series converge? a. I only

Question 5. Which of the following series converge?

a. I only b.

II only c. III only
d. I and II only e. II and III only

Solution: For series III:

Hence, series III diverges.

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a. I only b. II only c. III only d. I

a. I only b. II only c. III only
d. I and II only e.

II and III only

The sequence cos(k) diverges as

Hence, the sequence

does not converge to 0 as

Therefore, series II diverges.

In series II:

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Important series. This series converges if q > 1, and it diverges if

Important series.

This series converges if q > 1, and it diverges

if
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Question 5. A certain ball has the property that each time

Question 5. A certain ball has the property that each time

it falls from a height h onto a hard, level surface, it rebounds to a height rh, where 0 < r < 1.
Suppose that the ball is dropped from an initial height of H meters.
a) Assuming that the ball continues to bounce indefinitely, find the total distance that it travels.

Solution:

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«Ацкок» 2 A bouncing ball – total distance travelled

«Ацкок»

2

A bouncing ball – total distance travelled

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Question 7. A certain ball has the property that each time

Question 7. A certain ball has the property that each time

it falls from a height h onto a hard, level surface, it rebounds to a height r h, where 0 < r < 1.
Suppose that the ball is dropped from an initial height of H meters.
b) Calculate the total time that the ball spends bouncing.
Hint: A ball having zero velocity falls ½ gt2 meters in t seconds.

Solution: Actually, philosophers might find it obvious that the ball never stop bouncing.

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«Ацкок» 2 A bouncing ball – total bouncing time

«Ацкок»

2

A bouncing ball – total bouncing time

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Question 7. c) Suppose that each time the ball strikes the

Question 7. c) Suppose that each time the ball strikes the

surface with velocity v, it rebounds with velocity – kv, where 0 < k < 1.
How long will it take for the ball to come to rest?

Solution:

The velocity of the ball when it hits the ground for the first time is given by

where