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Problem
Problem
If
f
(
x
)
=
cos
(
log
x
)
f(x) = \cos(\log x)
f
(
x
)
=
cos
(
lo
g
x
)
, then
f
(
x
)
f
(
y
)
−
1
2
[
f
(
x
/
y
)
+
f
(
x
y
)
]
=
f(x)f(y) - \frac{1}{2}[f(x/y) + f(xy)] =
f
(
x
)
f
(
y
)
−
2
1
[
f
(
x
/
y
)
+
f
(
x
y
)]
=
a.
−
1
-1
−
1
b.
1
2
\frac{1}{2}
2
1
c.
−
2
-2
−
2
d. None of these
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