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National High School Mathematics League
1991 National High School Mathematics League
7
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Calculation
Source: 1991 National High School Mathematics League, Exam One, Problem 7
February 26, 2020
Problem Statement
cos
2
1
0
∘
+
cos
2
50
−
sin
4
0
∘
⋅
sin
8
0
∘
\cos^210^{\circ}+\cos^250-\sin40^{\circ}\cdot\sin80^{\circ}
cos
2
1
0
∘
+
cos
2
50
−
sin
4
0
∘
⋅
sin
8
0
∘
=________.
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