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★ 5/10
A Cosine Sum
Evaluate
cos
48
∘
−
cos
12
∘
+
cos
36
∘
.
\cos 48^\circ - \cos 12^\circ + \cos 36^\circ.
cos
4
8
∘
−
cos
1
2
∘
+
cos
3
6
∘
.
trigonometry
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