Westonci.ca is your go-to source for answers, with a community ready to provide accurate and timely information. Experience the convenience of finding accurate answers to your questions from knowledgeable professionals on our platform. Get precise and detailed answers to your questions from a knowledgeable community of experts on our Q&A platform.

a. Expand f(x) = In(z) centered at c = 1 using Taylor series.
b. With the aid of Maclaurin series, find the solution of the function f(x)=sin(x)


Sagot :

Sure, let's tackle each part of the question step-by-step.

### Part (a): Expand [tex]\( f(z) = \ln(z) \)[/tex] Centered at [tex]\( c = 1 \)[/tex] Using Taylor Series

To expand [tex]\( f(z) = \ln(z) \)[/tex] around [tex]\( z = 1 \)[/tex] using the Taylor series, we consider the series:

[tex]\[ f(z) = \sum_{n=0}^{\infty} \frac{f^{(n)}(1)}{n!} (z - 1)^n \][/tex]

where [tex]\( f^{(n)} \)[/tex] denotes the n-th derivative of [tex]\( f \)[/tex] evaluated at [tex]\( z=1 \)[/tex].

- For [tex]\( n = 0 \)[/tex], [tex]\( f(1) = \ln(1) = 0 \)[/tex]
- For [tex]\( n = 1 \)[/tex], [tex]\( f'(z) = \frac{1}{z} \)[/tex] and [tex]\( f'(1) = 1 \)[/tex]
- For [tex]\( n = 2 \)[/tex], [tex]\( f''(z) = -\frac{1}{z^2} \)[/tex] and [tex]\( f''(1) = -1 \)[/tex]
- For [tex]\( n = 3 \)[/tex], [tex]\( f'''(z) = \frac{2}{z^3} \)[/tex] and [tex]\( f'''(1) = 2 \)[/tex]
- And so on...

Following this pattern, we can write the first few terms of the Taylor series expansion:

[tex]\[ \ln(z) \approx (z - 1) - \frac{(z - 1)^2}{2} + \frac{(z - 1)^3}{3} - \frac{(z - 1)^4}{4} + \cdots \][/tex]

The expansion up to the 9th term is:

[tex]\[ \ln(z) \approx -1 - \frac{(z - 1)^2}{2} + \frac{(z - 1)^3}{3} - \frac{(z - 1)^4}{4} + \frac{(z - 1)^5}{5} - \frac{(z - 1)^6}{6} + \frac{(z - 1)^7}{7} - \frac{(z - 1)^8}{8} + \frac{(z - 1)^9}{9} + z + O((z-1)^{10}) \][/tex]

The above expression provides us the Taylor series expansion of [tex]\( \ln(z) \)[/tex] around [tex]\( z = 1 \)[/tex].

### Part (b): Using Maclaurin Series for [tex]\( f(x) = \sin(x) \)[/tex]

The Maclaurin series for a function [tex]\( f(x) \)[/tex] is a special case of the Taylor series centered at [tex]\( x = 0 \)[/tex]. For [tex]\( f(x) = \sin(x) \)[/tex], the series is:

[tex]\[ f(x) = \sum_{n=0}^{\infty} \frac{f^{(n)}(0)}{n!} x^n \][/tex]

The sine function is an odd function, so only odd powers of [tex]\( x \)[/tex] appear in its series expansion. Its derivatives alternate in a specific pattern due to the trigonometric properties:

- [tex]\( f(0) = \sin(0) = 0 \)[/tex]
- [tex]\( f'(0) = \cos(0) = 1 \)[/tex]
- [tex]\( f''(0) = -\sin(0) = 0 \)[/tex]
- [tex]\( f'''(0) = -\cos(0) = -1 \)[/tex]
- [tex]\( f^{(4)}(0) = \sin(0) = 0 \)[/tex]
- And so on...

Thus, the Maclaurin series for [tex]\( \sin(x) \)[/tex] is:

[tex]\[ \sin(x) \approx x - \frac{x^3}{6} + \frac{x^5}{120} - \frac{x^7}{5040} + \frac{x^9}{362880} + O(x^{10}) \][/tex]

This expansion provides us with the Maclaurin series of [tex]\( \sin(x) \)[/tex] up to the 9th power of [tex]\( x \)[/tex].

Together, these expansions answer both parts of the question comprehensively.