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7
Math Prize 2021 Problem 7
Math Prize 2021 Problem 7
Source:
September 19, 2021
Math Prize for Girls
Problem Statement
Compute the value of the infinite series
∑
k
=
0
∞
cos
(
k
π
/
4
)
2
k
.
\sum_{k=0}^{\infty} \frac{\cos(k \pi / 4)}{2^k} \, .
k
=
0
∑
∞
2
k
cos
(
kπ
/4
)
.
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