tan20°+4sin20°的值为______.-数学

题目简介

tan20°+4sin20°的值为______.-数学

题目详情

tan20°+4sin20°的值为______.
题型:填空题难度:中档来源:不详

答案

tan20°+4sin20°=class="stub"sin20°+4sin20°cos20°
cos20°

=class="stub"sin20°+2sin40°
cos20°

=
(sin20°+sin40°)+sin40°
cos20°

=class="stub"2sin30°cos10°+sin40°
cos20°

=class="stub"cos10°+sin40°
cos20°

=class="stub"sin80°+sin40°
cos20°

=class="stub"2sin60°cos20°
cos20°

=2sin60°=
3

故答案为:
3

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