Cos10°cos50°cos70°=
来源:学生作业帮 编辑:拍题作业网作业帮 分类:数学作业 时间:2024/05/19 22:47:01
Cos10°cos50°cos70°=
有没有简单一点的方法,我不想用积化和差
有没有简单一点的方法,我不想用积化和差
用积化和差做
cos10°cos50°cos70°
=0.5*{cos(10°+50°)+cos(10°-50°)}*cos70°
=0.5(cos60°+cos40°)cos70°
=0.5(0.5+cos40°)cos70°
=0.25*cos70°+0.5*cos40°cos70°
=0.25*cos70°+0.5*0.5{cos(40°+70°)+cos(40°-70°)}
=0.25*cos70°+0.25[cos110°+cos30°]
=0.25(cos70°+cos110°+cos30°)
因为cos70°=cos(180°-110°)=-cos110°
所以cos70°+cos110°=0
所以原式=0.25*cos30°=八分之根号三
cos10°cos50°cos70°
=0.5*{cos(10°+50°)+cos(10°-50°)}*cos70°
=0.5(cos60°+cos40°)cos70°
=0.5(0.5+cos40°)cos70°
=0.25*cos70°+0.5*cos40°cos70°
=0.25*cos70°+0.5*0.5{cos(40°+70°)+cos(40°-70°)}
=0.25*cos70°+0.25[cos110°+cos30°]
=0.25(cos70°+cos110°+cos30°)
因为cos70°=cos(180°-110°)=-cos110°
所以cos70°+cos110°=0
所以原式=0.25*cos30°=八分之根号三
(2cos70°+根号3sin10°)/cos10°
数学函数化简题2cos10°-sin20°/cos20°=?sin40°+2cos70°/sin50°=?
求值:2sin50°+cos10°*(1+根号3tan10°)/cs35°cos40°+cos50°cos55°
化简求值2sin50°+cos10°(1+3tan10°)cos35°cos40°+cos50°cos55°
sin70°-cos70°/sin70°+cos70°=多少啊
sin50°=a cos40°=?cos50°?
三角函数之求值问题sin²20°+cos²50°+sin20°cos50°=sin20°cos50
计算1sin50°+3cos50°
求cos20°cos10
2sin50°cos50°怎么等于cos50°cos40°+sin50°sin40°
1、求证:cos40°(cos10°+√3 sin10°)=cos10°
(sin40°cos50°+sin50°cos40°)=1 怎么等于1的啊