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Swedish Mathematical Competition
1983 Swedish Mathematical Competition
2
2
Part of
1983 Swedish Mathematical Competition
Problems
(1)
cos x^2 + cos y^2 - cos xy < 3
Source: 1983 Swedish Mathematical Competition p2
3/28/2021
Show that
cos
x
2
+
cos
y
2
−
cos
x
y
<
3
\cos x^2 + \cos y^2 - \cos xy < 3
cos
x
2
+
cos
y
2
−
cos
x
y
<
3
for reals
x
x
x
,
y
y
y
.
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trigonometry