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Problems
Contests
National and Regional Contests
Spain Contests
Spain Mathematical Olympiad
1986 Spain Mathematical Olympiad
6
6
Part of
1986 Spain Mathematical Olympiad
Problems
(1)
\prod_{k=1}^{14} cos (k\pi /15)
Source: Spanish Mathematical Olympiad 1986 P6
8/2/2018
Evaluate
∏
k
=
1
14
c
o
s
(
k
π
15
)
\prod_{k=1}^{14} cos \big(\frac{k\pi}{15}\big)
k
=
1
∏
14
cos
(
15
kπ
)
Product
trigonometry
geometry