Series Proof Help: Proving |ln 2| & |sin x|

In summary, to prove |ln 2|, use the definition of absolute value and the properties of logarithms. To prove |sin x|, use the properties of absolute value and trigonometric identities. When proving series, clearly state the series and use methods like mathematical induction and known series to simplify the proof. To use limits to prove series, use the definition and properties of limits. Proving series is important for determining convergence or divergence and building a deeper understanding of mathematical concepts.
  • #1
emc92
33
0
(1) Show that |ln 2 - ƩNn=1 ((-1)n-1)(1/n)| ≤ 1/(N+1)
(2) Show that |sin x - ƩNn=0 ((-1)n)/(2n+1)!| ≤ |x|2N+2/(2N+2)!


I really don't know where to start. should I change the sums to series first then work my way through? Please help!
 
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  • #2
Those are alternating series. The error bound is just the next element of the series.
 
  • #3
ohhhhh wow now i see. thanks so much!
 

1. How do I prove |ln 2|?

To prove |ln 2|, you need to use the definition of absolute value and the properties of logarithms. First, write ln 2 as ln(2) and then use the property ln(a) = b if and only if e^b = a. This will help you to simplify the expression and prove that |ln 2| = ln 2.

2. Can you explain how to prove |sin x|?

To prove |sin x|, you can use the properties of absolute value and trigonometric identities. One approach is to use the identity |sin x| = √(sin^2x). Then, you can use the Pythagorean identity sin^2x + cos^2x = 1 to simplify the expression and prove that |sin x| = sin x.

3. Are there any tips for proving series?

Yes, there are a few tips for proving series. First, make sure to clearly state the series you are trying to prove and the value it is equal to. Then, use mathematical induction or other methods to show that the series is convergent. Additionally, it can be helpful to use known series and their properties to simplify the series you are trying to prove.

4. How can I use limits to prove series?

To use limits to prove series, you can use the definition of a limit and properties of limits. For example, you can use the limit comparison test or the ratio test to show that the limit of the series is equal to a known value, which proves the series is convergent.

5. What is the importance of proving series?

Proving series is important because it helps to determine the convergence or divergence of a series, which can have real-world applications in fields such as physics, engineering, and finance. It also helps to build a better understanding of mathematical concepts and their properties.

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