r
α
1
.
0
5
O
D
=
O
B
+
B
C
+
C
D
O
B
=
(
r
.
ω
)
ω
B
C
=
(
r
-
(
r
.
ω
)
ω
)
c
o
s
(
α
)
C
D
=
ω
×
r
s
i
n
(
α
)