cos20+cos60+cos100+cos140
求值
人气：460 ℃ 时间：2020-04-08 13:58:30
解答
原式=cos20+cos60+cos(120-20)+cos(120+20)
=cos20+cos60+cos120cos20+sin120sin20+cos120cos20-sin120sin20
=cos20+cos60+2cos120cos20
=cos20+cos60-cos20
=cos60
=1/2
推荐
- 数学cos20+cos60+cos100+cos140=?
- cos20°-cos40°+cos60°+cos100°的值等于 _．
- cos20°-sin40°+cos60°+cos100°
- 已知logaX=1/cos20°,logbX=1/cos60°,logcX=1/cos100°,logdX=1/cos140°,求logabcdX的值
- cos20°+cos100度+cos140度=?
- WE COULDN'T CHOOSE WHERE WE WILL BE BORN.这句话对吗?
- 集合A.B定义A-B={x|x∈A,且x￠B},A*B=(A-B)∪(B-A)若A={1,3,5}B={3,5,7,9}则A*B=
- 数学中心对称图形定理
猜你喜欢
