cos20°-cos40°-cos80°=
答案:2 悬赏:20 手机版
解决时间 2021-03-13 02:05
- 提问者网友：火车头
- 2021-03-12 06:17
cos20°-cos40°-cos80°=
最佳答案
- 五星知识达人网友：胯下狙击手
- 2021-03-12 06:29
cos40+cos80
=cos(60-20)+cos60+20)
=cos60cos20+sin60sin20+cos60cos20-sin60sin20
=2cos60cos20
=2*1/2*cos20
=cos20
cos20-cos40-cos80=cos20-cos20=0
=cos(60-20)+cos60+20)
=cos60cos20+sin60sin20+cos60cos20-sin60sin20
=2cos60cos20
=2*1/2*cos20
=cos20
cos20-cos40-cos80=cos20-cos20=0
全部回答
- 1楼网友：执傲
- 2021-03-12 06:37
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-[cos(60-20)+cos(60+20)]
=cos20-[(cos60c0s20+sin60sin20)+(cos60cos20-sin60sin20)]
=cos20-2cos60cos20
=cos20-2*1/2*cos20
=cos20-cos20
=0
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