sin10°+2sin10°sin20°sin40°=______.
来源:学生作业帮 编辑:搜搜做题作业网作业帮 分类:数学作业 时间:2024/07/14 07:15:47
sin10°+2sin10°sin20°sin40°=______.
![sin10°+2sin10°sin20°sin40°=______.](/uploads/image/z/17958363-51-3.jpg?t=sin10%C2%B0%2B2sin10%C2%B0sin20%C2%B0sin40%C2%B0%3D______%EF%BC%8E)
原式=sin10°+2sin10°•[
cos(20°−40°)
2-
cos(20°+40°)
2-]
=sin10°+sin10°•(cos20°-cos60°)
=sin10°-
1
2sin10°+sin10°cos20°
=
1
2sin10°+sin10°cos20°
=
1
2[sin(10°-20°)+sin(10°+20°)]+
1
2sin10°
=-
1
2sin10°+
1
4+
1
2sin10°
=
1
4,
故答案为:
1
4
cos(20°−40°)
2-
cos(20°+40°)
2-]
=sin10°+sin10°•(cos20°-cos60°)
=sin10°-
1
2sin10°+sin10°cos20°
=
1
2sin10°+sin10°cos20°
=
1
2[sin(10°-20°)+sin(10°+20°)]+
1
2sin10°
=-
1
2sin10°+
1
4+
1
2sin10°
=
1
4,
故答案为:
1
4
sin10°^2+cos40°^2+sin10°sin40°
sin40°*(1-sin10°)/[sin10°*(cos20°)^2]
sin10°+sin20°+sin30°+sin40°+sin50°+……+sin2000°=?
sin40°cos10°-cos40°sin10°
sin20°×cos7o°+sin10°×sin50°的值
sin20°cos70°+sin10°sin50°
sin20°cos70°+sin10°sin50°等于
(cos10°-根号3sin10°)/sin20°
sin10°+sin20°+sin40°+sin50°+sin70°+sin80°求步骤加答案各方学霸求解答谢谢啦!
(sin10°+sin20°cos30°)/(cos10°-sin20°sin30°) 值
化简((cos20°/sin20°)cos10°)+根号3(sin10°tan70°)-2cos40°
cos10°-根号3sin10°/sin20°=?要求用辅助角公式做!