sin15度cos165度的值是?
发布网友
共2个回答
热心网友
sin2A=2sinA·cosA
sin15度cos165度=sin15cos(180-15)
=-sin15cos15
=-1/2sin30
=-1/4
热心网友
sin(15)cos(165)=sin(15)cos(180-15)= -sin(15)cos(-15)= -sin(15)cos(15)= (- 1/2) *sin30= (-1/4)
