MathDB

7

Part of 1991 National High School Mathematics League

Problems(1)

Calculation

Source: 1991 National High School Mathematics League, Exam One, Problem 7

2/26/2020
cos⁡210∘+cos⁡250−sin⁡40∘⋅sin⁡80∘\cos^210^{\circ}+\cos^250-\sin40^{\circ}\cdot\sin80^{\circ}=________.