来自刘心田的问题
【已知sin(a+π/12)=1/3,则cos(a+7π/12)的值等于】
已知sin(a+π/12)=1/3,则cos(a+7π/12)的值等于
1回答
2020-04-05 09:01
【已知sin(a+π/12)=1/3,则cos(a+7π/12)的值等于】
已知sin(a+π/12)=1/3,则cos(a+7π/12)的值等于
cos(a+7π/12)
=cos[(a+π/12)+π/2]
=cos(a+π/12)cos(π/2)-sin(a+π/12)sin(π/2)
=0-1/3*1
=-1/3