化简 sin119°sin181°-sin91°sin29°= 写个过程啊~

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化简sin119°sin181°-sin91°sin29°=写个过程啊~化简sin119°sin181°-sin91°sin29°=写个过程啊~化简sin119°sin181°-sin91°sin29

化简 sin119°sin181°-sin91°sin29°= 写个过程啊~
化简 sin119°sin181°-sin91°sin29°= 写个过程啊~

化简 sin119°sin181°-sin91°sin29°= 写个过程啊~
原式=sin(180-61)sin(180+1)-sin(180-89)sin29
=-sin61sin1-sin89sin29
=-[sin(90-29)sin1+cos(90-89)sin29]
=-(cos29sin1+cos1sin29)
=-sin(1+29)
=-sin30
=-1/2