s
i
n
(
2
α
)
=
s
i
n
(
α
+
α
)
=
s
i
n
(
α
)
c
o
s
(
α
)
+
c
o
s
(
α
)
s
i
n
(
α
)
=
2
s
i
n
(
α
)
c
o
s
(
α
)
s
i
n
(
2
α
)
=
s
i
n
(
α
+
α
)
=
s
i
n
(
α
)
c
o
s
(
α
)
+
c
o
s
(
α
)
s
i
n
(
α
)
=
2
s
i
n
(
α
)
c
o
s
(
α
)