sin164sin224+sin254sin314化简这道题应该要怎么做,
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sin164sin224+sin254sin314化简这道题应该要怎么做,
如题
如题
![sin164sin224+sin254sin314化简这道题应该要怎么做,](/uploads/image/z/2321477-53-7.jpg?t=sin164sin224%2Bsin254sin314%E5%8C%96%E7%AE%80%E8%BF%99%E9%81%93%E9%A2%98%E5%BA%94%E8%AF%A5%E8%A6%81%E6%80%8E%E4%B9%88%E5%81%9A%2C)
sin164°sin224°+sin254°sin314°
=sin16°(-sin44°)+(-sin74°)(-sin46°)
=sin74°sin46°-sin16°sin44°
=sin74°cos44°-cos74°sin44°
=sin(74°-44°)
=sin30
=1/2
=sin16°(-sin44°)+(-sin74°)(-sin46°)
=sin74°sin46°-sin16°sin44°
=sin74°cos44°-cos74°sin44°
=sin(74°-44°)
=sin30
=1/2