> 数学 >
sin10°^2+cos40°^2+sin10°sin40°
人气:150 ℃ 时间:2020-03-30 18:16:57
解答
sin10°^2+cos40°^2+sin10°sin40°
=1/2(1-cos20)+1/2(1+cos80)+1/2(cos20-cos60)
=3/4+1/2*cos80
题目估计抄错了
估计是这样:
sin10°^2+cos40°^2+sin10°cos40°
=1/2(1-cos20)+1/2(1+cos80)+1/2(sin50-sin30)
=3/4-1/2(cos20-cos80)+1/2sin50
=3/4-sin30*sin50+1/2sin50
=3/4
推荐
猜你喜欢
© 2024 79432.Com All Rights Reserved.
电脑版|手机版