What is the general term $(a_n)$ of the alternating sequence $\displaystyle \cos \left( \frac{3n \pi}{2} \right)$ from $1$ to $\infty$, $n \in \mathbb{N}$ ?
What is the general term $(a_n)$ of the alternating sequence $\cos(3n \pi/2)$?
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calculus
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1Does t = n? Have you tried evaluating a few terms yourself? – 2011-01-04
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0This is alternating, and furthermore it is periodic with 4t. This should be enough for solving that... – 2011-01-04
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0$cos(3t \pi/2): cos(3 \pi/2)=0, cos(3\pi)=-1, cos(9 \pi/2)=0, cos(6 \pi) = 1 \cdots$, but general rule is missing in my mind. – 2011-01-04