tan20°+4sin20°的值为______．
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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 ．
= 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 ．
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