题目应该是
sin22°+ cos30°sin8°
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cos22°- sin30°sin8°
sin22`=sin(30`-8`)=sin30`*cos8`-cos30`*sin8`
sin22°+ cos30°sin8°=sin30`*cos8`
cos22`=cos(30`-8`)=sin30`*sin8`+cos30`*cos8`
cos22°- sin30°sin8°=cos30`*cos8`
分子除以分母得：sin30`*cos8`/cos30`*cos8`=sin30`/cos30`=根号3除以3