Which of the following power series equals for all real ?

MATHEMATICS · Single correct · AP · Calculus BC · Infinite Sequences and Series · Infinite Sequences and Series

Problem

Which of the following power series equals sin⁡x\sin x for all real xx? (a) ∑n=0∞(−1)nx2n(2n)!\displaystyle \sum_{n=0}^{\infty}(-1)^n\dfrac{x^{2n}}{(2n)!} (b) ∑n=0∞(−1)nx2n+1(2n+1)!\displaystyle \sum_{n=0}^{\infty}(-1)^n\dfrac{x^{2n+1}}{(2n+1)!} (c) ∑n=0∞(−1)nx2n+1(2n)!\displaystyle \sum_{n=0}^{\infty}(-1)^n\dfrac{x^{2n+1}}{(2n)!} (d) ∑n=0∞x2n+1(2n+1)!\displaystyle \sum_{n=0}^{\infty}\dfrac{x^{2n+1}}{(2n+1)!}

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