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So we had two examples in class, but I don't understand why they're different. And the professor is away today, which means I won't see him until the entire weekend has passed (a nightmare for students like me who obsess over a problem).
1. For which x is the approximation sin(x) ≈ x - (x^3)/6 correct within 1/100?
The Taylor series for sin(x):
x - (x^3)/3! + (x^5)/5! - (x^7)/7! + ...
The answer was, For every x not equal to 0, this is an alternating series. Thus the error in sin(x) ≈ x - (x^3)/3! is no larger than |(x^5)/5!|. So |(x^5)/5!| < 1/100. 2. For which x is the approximation sin(x) = x - x^3/6 correct within 1/1000?
My professor took the 3 order polynomial for the Taylor Series of sin(x) and used the Remainder Theorem:
R3(x) = (f4c)(x-0)4/4!
f(x) = sin(x)
f1(x) = cos(x)
f2(x) = -sin(x)
f3(x) = -cos(x)
f4(x) = sin(x)
So |sin(c)| ≤ 1
|R3(x)| ≤ |x|4/4!
Answer: |x|4/4! ≤ 1/1000I don't understand why they used Remainder Theorem for the second one. Yes, I know the 1/100 and 1/1000 are different But why is the approach different?
1. For which x is the approximation sin(x) ≈ x - (x^3)/6 correct within 1/100?
The Taylor series for sin(x):
x - (x^3)/3! + (x^5)/5! - (x^7)/7! + ...
The answer was, For every x not equal to 0, this is an alternating series. Thus the error in sin(x) ≈ x - (x^3)/3! is no larger than |(x^5)/5!|. So |(x^5)/5!| < 1/100. 2. For which x is the approximation sin(x) = x - x^3/6 correct within 1/1000?
My professor took the 3 order polynomial for the Taylor Series of sin(x) and used the Remainder Theorem:
R3(x) = (f4c)(x-0)4/4!
f(x) = sin(x)
f1(x) = cos(x)
f2(x) = -sin(x)
f3(x) = -cos(x)
f4(x) = sin(x)
So |sin(c)| ≤ 1
|R3(x)| ≤ |x|4/4!
Answer: |x|4/4! ≤ 1/1000I don't understand why they used Remainder Theorem for the second one. Yes, I know the 1/100 and 1/1000 are different But why is the approach different?
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