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Mathematics
Mathematics
Problem
Show that
sin
x
+
sin
3
x
+
sin
5
x
+
sin
7
x
=
4
sin
4
x
cos
2
x
cos
x
\sin x + \sin 3x + \sin 5x + \sin 7x = 4 \sin 4x \cos 2x \cos x
sin
x
+
sin
3
x
+
sin
5
x
+
sin
7
x
=
4
sin
4
x
cos
2
x
cos
x
.
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