早教吧作业答案频道 -->数学-->
已知sin(x+30°）=1/4,求sin（210°+x）+cos²（150°-x）的值
题目详情
已知sin(x+30°）=1/4,求sin（210°+x）+cos²（150°-x）的值
▼优质解答
答案和解析
sin(210°+x)+[cos(150°-x)]^2
=-sin(30°+x)+[cos(-30°-x)]^2
=-1/4+[cos(30°+x)]^2
=-1/4+1-[sin(30°+x)]^2
=-1/4+1-(1/4)^2
=3/4-1/16
=11/16
=-sin(30°+x)+[cos(-30°-x)]^2
=-1/4+[cos(30°+x)]^2
=-1/4+1-[sin(30°+x)]^2
=-1/4+1-(1/4)^2
=3/4-1/16
=11/16
看了 已知sin(x+30°）=1...的网友还看了以下：