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J
Lv 7
J asked in Science & MathematicsMathematics · 3 years ago

What is the sum from n=1 to ∞ of (-1)^(n+1) π^(2n) / (2n+1)!?

2 Answers

Relevance
  • 3 years ago
    Favorite Answer

    sin(x) = sum from n=0 to ∞ of (-1)^n x^(2n+1) / (2n+1)!

    So the series in question is equal to

    1-sin(x)/x , evaluated for x = π

    = 1 - sin(π)/π = 1 - 0/π = 1

    So the answer is 1.

  • 3 years ago

    The alternating series converges as T(n)->0 as n->infinity.

    The sum is

    S=(pi^2)/3!+(pi^4)/5!+(pi^6)/7!+(pi^8)/9!+R(4), where R(4)=the remainder after the first 4 terms.

    =>

    S<0.997795618+|pi^10/11!|

    =>

    S<0.997795618+0.002346081

    =>

    S<1.000141699

    =>

    S=1 as n->infinity.

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