问题
填空题
tan20°+4sin20°的值为______．
答案
tan20°+4sin20°=sin20°+4sin20°cos20° cos20°
=sin20°+2sin40° cos20°
=(sin20°+sin40°)+sin40° cos20°
=2sin30°cos10°+sin40° cos20°
=cos10°+sin40° cos20°
=sin80°+sin40° cos20°
=2sin60°cos20° cos20°
=2sin60°=
．3
故答案为：
．3