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Mathematics
Mathematics
Problem
Which of the following expressions is identically equal to
cos
x
\cos x
cos
x
for all real
x
x
x
? a)
sin
(
x
−
π
2
)
\sin\left(x-\dfrac{\pi}{2}\right)
sin
(
x
−
2
π
)
b)
cos
(
x
−
π
2
)
\cos\left(x-\dfrac{\pi}{2}\right)
cos
(
x
−
2
π
)
c)
sin
(
x
+
π
2
)
\sin\left(x+\dfrac{\pi}{2}\right)
sin
(
x
+
2
π
)
d)
−
sin
(
x
+
π
2
)
-\sin\left(x+\dfrac{\pi}{2}\right)
−
sin
(
x
+
2
π
)
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