c
o
s
(
γ
)
=
2
c
o
s
2
(
γ
2
)
−
1
c
o
s
(
γ
)
=
1
−
2
s
i
n
2
(
γ
2
)
c
o
s
(
γ
)
=
2
c
o
s
2
(
γ
2
)
−
1
c
o
s
(
γ
)
=
1
−
2
s
i
n
2
(
γ
2
)
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