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Byju's Answer
Standard XII
Mathematics
Sin(A+B)Sin(A-B)
If A+B+C=π,...
Question
If
A
+
B
+
C
=
π
, show that
sin
(
A
2
)
+
sin
(
B
2
)
+
sin
(
C
2
)
=
1
+
4
sin
π
−
A
4
sin
π
−
B
4
sin
π
−
C
4
.
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Solution
L.H.S.
=
2
sin
A
+
B
4
cos
A
−
B
4
+
cos
(
π
2
−
C
2
)
=
2
sin
π
−
C
4
cos
A
−
B
4
+
1
−
2
sin
2
π
−
C
4
=
1
+
2
sin
π
−
C
4
[
cos
A
−
B
4
−
sin
A
+
B
4
]
by
(
1
)
=
1
+
2
sin
π
−
C
4
[
cos
A
−
B
4
−
cos
(
π
2
−
A
+
B
4
)
]
=
1
+
2
sin
π
−
C
4
[
2
sin
π
−
B
4
sin
π
−
A
4
]
=
1
+
4
sin
π
−
A
4
sin
π
−
B
4
sin
π
−
C
4
.
Suggest Corrections
1
Similar questions
Q.
If
A
+
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+
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=
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, then prove that
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If
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Standard XII Mathematics
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