化简1+sin40°-cos40°/1+sin40°+cos40°

问题描述:

化简1+sin40°-cos40°/1+sin40°+cos40°

1+sin40-cos40=1+2sin20cos20-(1-2sin²20)=2sin20cos20+2sin²20=2sin20(sin20+cos20)1+sin40+cos40=1+2sin20cos20+2cos²20-1=2cos20(sin20+cos20)(1+sin40-cos40)/(1+sin40+cos40)=2sin20(sin20+cos2...