cos2@=(cos@)^2-(sin@)^2=(cos@-sin@)(cos@+sin@)
sin(@-45)=sin@cos45-cos@sin45=二分之根号二(sin@-cos@)
所以
(cos2@)除以sin(@-45度)= - (cos@+sin@ ) /(二分之根号二)=负二分之根号二
=> (cos@+sin@ )=1/2
若(cos2@)除以sin(@-45度)=负二分之根号二.则cos@+sin@的值为多少
若(cos2@)除以sin(@-45度)=负二分之根号二.则cos@+sin@的值为多少
数学人气:981 ℃时间:2020-05-24 20:56:43
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