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Problem
Problem
Let
α
\alpha
α
be a real number such that
0
≤
α
≤
π
0 \le \alpha \le \pi
0
≤
α
≤
π
. If
f
(
x
)
=
cos
x
+
cos
(
x
+
α
)
+
cos
(
x
+
2
α
)
f(x) = \cos x + \cos(x + \alpha) + \cos(x + 2\alpha)
f
(
x
)
=
cos
x
+
cos
(
x
+
α
)
+
cos
(
x
+
2
α
)
takes some constant number
c
c
c
for any
x
∈
R
x \in R
x
∈
R
, then the value of
[
c
+
α
]
[c + \alpha]
[
c
+
α
]
is equal to Note
[
y
]
[y]
[
y
]
denotes greatest integer less than or equal to
y
y
y
. a. 0 b. 1 c. -1 d. 2
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