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Mathematics
Problem
State the identity that expresses
cos
(
x
−
y
)
\cos(x-y)
cos
(
x
−
y
)
in terms of
cos
x
,
cos
y
,
sin
x
\cos x,\cos y,\sin x
cos
x
,
cos
y
,
sin
x
and
sin
y
\sin y
sin
y
.
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