作业帮cos20°-cos40°-cos80°=
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cos20°-cos40°-cos80°=
cos20°-cos40°-cos80°=
cos20°-cos40°-cos80°=
cos40+cos80
=cos(60-20)+cos60+20)
=cos60cos20+sin60sin20+cos60cos20-sin60sin20
=2cos60cos20
=2*1/2*cos20
=cos20
cos20-cos40-cos80=cos20-cos20=0
0
cos20-(cos40+cos80)
=cos20-[cos(60-20)+cos(60+20)]
=cos20-[(cos60c0s20+sin60sin20)+(cos60cos20-sin60sin20)]
=cos20-2cos60cos20
=cos20-2*1/2*cos20
=cos20-cos20
=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°=
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°=______
(sin20°×cos20°×cos40°×cos60°×cos80°)÷sin20°
求cos20°cos40°cos80°sin10°sin50°sin70°
化简求值：cos10°*cos20°*cos40°*cos80°*cos160°