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Mathematics
Mathematics
Problem
In a
Δ
A
B
C
\Delta ABC
Δ
A
B
C
, prove that
∑
r
=
0
n
n
C
r
a
r
b
n
−
r
cos
(
r
B
−
(
n
−
r
)
A
)
=
c
n
.
\sum_{r=0}^{n} {}^n C_r a^r b^{n-r} \cos(rB - (n-r)A) = c^n.
r
=
0
∑
n
n
C
r
a
r
b
n
−
r
cos
(
r
B
−
(
n
−
r
)
A
)
=
c
n
.
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