为什么:sinA -√3cosA=2sin(a-π/3)?
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为什么:sinA -√3cosA=2sin(a-π/3)?
为什么:sinA -√3cosA=2sin(a-π/3)?
为什么:sinA -√3cosA=2sin(a-π/3)?
首先要知道这个题利用了公式 sin(A-B)=sinAcosB-cosAsinB
创造条件,利用公式.
sinA -√3cosA
=2(1/2 sinA- √3/2 cosA)
=2(cosπ/3 sinA-sinπ/3cosA)
=2sin(A-π/3 )
sinA -√3cosA
=2(sinA*1/2-cosA*√3/2)
=2(sinAcosπ/3-cosAsinπ/3)
=2sin(A-π/3)