先计算sin50(1+√3tan10)的值:
sin50(1+√3tan10)
=sin50[1+√3(sin10/cos10)]
=sin50[(cos10+√3sin10)/cos10]
=sin50[2sin(30+10)/cos10]
=(2sin50sin40)/cos10°
=(2cos40°*sin40°)/cos10°
=sin80°/cos10°
=cos10°/cos10°
=1
所以[cos40+sin50(1+√3tan10)]/sin70√(1+sin50)
=[cos40+1]/[sin70√(1+sin50)]
=(2 cos²20)/[ cos20*√(sin25+cos25)²]
=(2 cos²20)/[ cos20*(sin25+cos25)]
=(2 cos20)/(sin25+cos25)
=(2 cos20)/[√2(sin25+45))
=(2 cos20)/[√2sin70]
=(2 cos20)/[√2cos20]
=√2.
[cos40+sin50(1+√3tan10)]/sin70√(1+sin50)
=[cos40+sin50(1+√3tan10)]/sin70√(1+cos40)
=[cos40+sin50(1+√3*sin10/cos10)]/sin70√(1+2cos²20-1)
=[cos40+sin50(cos10/cos10+√3*sin10/cos10)]/[sin70√(2cos²20)
=[cos40+sin50(cos10+√3*sin10)/cos10]/[√2(sin70cos20)]
=[cos40+2sin50(1/2*cos10+√3/2*sin10)/cos10]/[√2(cos20cos20)]
=[cos40+2sin50(sin30cos10+cos30sin10)/cos10]/[√2(cos²20)]
=[cos40+2sin50sin(30+10)/cos10]/[√2(cos²20)]
=[cos40+2sin50sin40/cos10]/[√2(cos²20)]
=[cos40+2cos40sin40/cos10]/[√2(cos²20)]
=[cos40+sin80/cos10]/[√2(cos²20)]
=[cos40+cos10/cos10]/[√2(cos²20)]
=(cos40+1)/[√2(cos²20)]
=(2cos²20-1+1)/[√2(cos²20)]
=(2cos²20)/[√2(cos²20)]
=2/√2
=2*√2/(√2*√2)
=√2