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Mathematics
Mathematics
Problem
Prove that
cos
18
∘
−
sin
18
∘
=
2
sin
27
∘
\cos 18^\circ - \sin 18^\circ = \sqrt{2}\sin 27^\circ
cos
1
8
∘
−
sin
1
8
∘
=
2
sin
2
7
∘
.
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