已知cos(π/6—α)=1/3.则cos(5/6π+α)· sin(2/3π-α)=?其中一步sin(2/3π-α)= sin[3π/2-(5π/6+α)]=-cos(5/6π+α)为什么sin[3π/2-(5π/6+α)]能化成 -cos(5/6π+α)
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![已知cos(π/6—α)=1/3.则cos(5/6π+α)· sin(2/3π-α)=?其中一步sin(2/3π-α)= sin[3π/2-(5π/6+α)]=-cos(5/6π+α)为什么sin[3π/2-(5π/6+α)]能化成 -cos(5/6π+α)](/uploads/image/z/1801869-69-9.jpg?t=%E5%B7%B2%E7%9F%A5cos%28%CF%80%EF%BC%8F6%E2%80%94%CE%B1%EF%BC%89%3D1%EF%BC%8F3.%E5%88%99cos%285%EF%BC%8F6%CF%80%2B%CE%B1%EF%BC%89%C2%B7+sin%282%EF%BC%8F3%CF%80-%CE%B1%29%3D%3F%E5%85%B6%E4%B8%AD%E4%B8%80%E6%AD%A5sin%282%EF%BC%8F3%CF%80-%CE%B1%29%3D+sin%5B3%CF%80%2F2-%285%CF%80%EF%BC%8F6%2B%CE%B1%29%5D%3D-cos%285%EF%BC%8F6%CF%80%2B%CE%B1%EF%BC%89%E4%B8%BA%E4%BB%80%E4%B9%88sin%5B3%CF%80%2F2-%285%CF%80%EF%BC%8F6%2B%CE%B1%29%5D%E8%83%BD%E5%8C%96%E6%88%90+-cos%285%EF%BC%8F6%CF%80%2B%CE%B1%EF%BC%89)
已知cos(π/6—α)=1/3.则cos(5/6π+α)· sin(2/3π-α)=?其中一步sin(2/3π-α)= sin[3π/2-(5π/6+α)]=-cos(5/6π+α)为什么sin[3π/2-(5π/6+α)]能化成 -cos(5/6π+α)
已知cos(π/6—α)=1/3.则cos(5/6π+α)· sin(2/3π-α)=?
其中一步
sin(2/3π-α)= sin[3π/2-(5π/6+α)]=-cos(5/6π+α)
为什么sin[3π/2-(5π/6+α)]能化成 -cos(5/6π+α)
已知cos(π/6—α)=1/3.则cos(5/6π+α)· sin(2/3π-α)=?其中一步sin(2/3π-α)= sin[3π/2-(5π/6+α)]=-cos(5/6π+α)为什么sin[3π/2-(5π/6+α)]能化成 -cos(5/6π+α)
sin[3π/2-(5π/6+α)]能化成 -cos(5/6π+α)
诱导公式sin(3π/2-a)=-cosa