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Mathematics
Mathematics
Problem
If
u
⃗
\vec{u}
u
and
v
⃗
\vec{v}
v
are unit vectors making angles
α
\alpha
α
and
β
\beta
β
respectively with the positive
x
x
x
–axis, then
u
⃗
⋅
v
⃗
\vec{u}\,\cdot\,\vec{v}
u
⋅
v
equals a)
sin
(
α
−
β
)
\sin(\alpha-\beta)
sin
(
α
−
β
)
b)
cos
(
α
−
β
)
\cos(\alpha-\beta)
cos
(
α
−
β
)
c)
cos
(
α
+
β
)
\cos(\alpha+\beta)
cos
(
α
+
β
)
d)
cos
α
cos
β
\cos\alpha\cos\beta
cos
α
cos
β
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