sin²20°+cos²50°+sin20°cos50°
答案:2 悬赏:70 手机版
解决时间 2021-11-29 14:06
- 提问者网友：浪荡绅士
- 2021-11-28 15:34
sin²20°+cos²50°+sin20°cos50°
最佳答案
- 五星知识达人网友：酒者煙囻
- 2021-11-28 15:50
解答：
sin²20°+cos²50°+sin20°cos50°
=(1-cos40°)/2+(1+cos100°)/2+(1/2)*(sin70°-sin30°)
=(1-cos40°)/2+(1-cos80°)/2+(1/2)*(cos20°-1/2)
=1-(1/2)*(cos40°+cos80°)+(1/2)*(cos20°-1/2)
=1-(cos60°cos20°)+(1/2)cos20°-1/4
=1-(1/2)cos20°+(1/2)cos20°-1/4
=3/4
sin²20°+cos²50°+sin20°cos50°
=(1-cos40°)/2+(1+cos100°)/2+(1/2)*(sin70°-sin30°)
=(1-cos40°)/2+(1-cos80°)/2+(1/2)*(cos20°-1/2)
=1-(1/2)*(cos40°+cos80°)+(1/2)*(cos20°-1/2)
=1-(cos60°cos20°)+(1/2)cos20°-1/4
=1-(1/2)cos20°+(1/2)cos20°-1/4
=3/4
全部回答
- 1楼网友：时间的尘埃
- 2021-11-28 16:12
这个答案怎么样？
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