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IMC
1996 IMC
8
8
Part of
1996 IMC
Problems
(1)
IMC 1996 Problem 8
Source: IMC 1996
3/4/2021
Let
θ
\theta
θ
be a positive real number. Show that if
k
∈
N
k\in \mathbb{N}
k
∈
N
and both
cosh
k
θ
\cosh k \theta
cosh
k
θ
and
cosh
(
k
+
1
)
θ
\cosh(k+1) \theta
cosh
(
k
+
1
)
θ
are rational, then so is
cosh
θ
\cosh \theta
cosh
θ
.
trigonometry