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Problem
Problem
In any triangle,
1
+
cos
(
A
−
B
)
cos
C
1
+
cos
(
A
−
C
)
cos
B
=
\frac{1 + \cos(A - B) \cos C}{1 + \cos(A - C) \cos B} =
1
+
c
o
s
(
A
−
C
)
c
o
s
B
1
+
c
o
s
(
A
−
B
)
c
o
s
C
=
a.
a
2
+
b
2
a
2
+
c
2
\frac{a^2 + b^2}{a^2 + c^2}
a
2
+
c
2
a
2
+
b
2
b.
b
2
+
c
2
b
2
−
c
2
\frac{b^2 + c^2}{b^2 - c^2}
b
2
−
c
2
b
2
+
c
2
c.
c
2
−
a
2
a
2
+
b
2
\frac{c^2 - a^2}{a^2 + b^2}
a
2
+
b
2
c
2
−
a
2
d. None of these
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