sin15度cos165度的值是?

来源:学生作业帮助网 编辑:六六作业网 时间:2024/11/17 19:03:35
sin15度cos165度的值是?sin15度cos165度的值是?sin15度cos165度的值是?sin2A=2sinA·cosAsin15度cos165度=sin15cos(180-15)=-s

sin15度cos165度的值是?
sin15度cos165度的值是?

sin15度cos165度的值是?
sin2A=2sinA·cosA
sin15度cos165度=sin15cos(180-15)
=-sin15cos15
=-1/2sin30
=-1/4

sin(15)cos(165)=sin(15)cos(180-15)= -sin(15)cos(-15)= -sin(15)cos(15)= (- 1/2) *sin30= (-1/4)