cos(α-35°)cos(α+25°)+sin(α-35°)sin(α+25°)怎么算
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cos(α-35°)cos(α+25°)+sin(α-35°)sin(α+25°)怎么算
![cos(α-35°)cos(α+25°)+sin(α-35°)sin(α+25°)怎么算](/uploads/image/z/19718785-1-5.jpg?t=cos%EF%BC%88%CE%B1-35%C2%B0%EF%BC%89cos%EF%BC%88%CE%B1%2B25%C2%B0%EF%BC%89%2Bsin%EF%BC%88%CE%B1-35%C2%B0%EF%BC%89sin%EF%BC%88%CE%B1%2B25%C2%B0%EF%BC%89%E6%80%8E%E4%B9%88%E7%AE%97)
原式 = cos [ (α -35°) -(α +25°) ]
= cos (-60°)
= cos 60°
= 1/2.
= = = = = = = = =
cos (A-B) =cos A cos B +sin A sin B,
cos (-A) =cos A.
= cos (-60°)
= cos 60°
= 1/2.
= = = = = = = = =
cos (A-B) =cos A cos B +sin A sin B,
cos (-A) =cos A.
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