(cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°=

来源：学生作业帮助网 编辑：作业帮 时间：2024/11/15 19:49:28
(cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°=
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(cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°=
(cos80°-cos20°)/sin80°+sin20°)=
顺便再回答个
cos20°+cos100°+cos140°=

(cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°=
(cos80°-cos20°)/(sin80°+sin20°)
=[cos(50°+30°)-cos(50°-30°)]/[sin(50°+30°)+sin(50°-30°)]
=[(cos50°cos30°-sin50°sin30°)- (cos50°cos30°+sin50°sin30°)]/[ (sin50°cos30°+cos50°sin30°)+ (sin50°cos30°-cos50°sin30°)]
=(-2sin50°sin30°)/ (2sin50°cos30°)
= -2sin30°/ cos30°
= -tan30°
= -√3/3
cos20°+cos100°+cos140°
= cos (80°-60°)+cos100°+cos(80°+60°)
= (cos80°cos60°+sin80°sin60°)+cos100°+ (cos80°cos60°-sin80°sin60°)
= 2cos80°cos60°+cos100°
= cos80°+cos100°
= cos80°-cos80°
=0

cos20°-cos40°-cos80°= cos20°cos40°cos80°=? 计算cos20°cos40°cos80° 化简cos20°cos40°cos60°cos80° cos20°*cos40°*cos60°*cos80°= cos20°cos40°cos60°cos80°是多少 不查表求:cos20°*cos40°*cos60°*cos80°= cos20°cos10°-cos70°cos80° cos80°cos20°+sin100°sin380°=? 化简cos20°-cos40°-cos80°等于? cos20°cos40°cos80°怎么算 cos20°cos40°cos80°的值、急 cos20°-cos40°-cos80°的值为? cos20°cos40°cos80°的值是 计算cos20°cos40°cos80°=多少 cos20°×cos40°×cos80°=______ cos20°+cos40°+cos80°=______ (cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°=