已知sin(x+30°）=1/4，求sin（210°+x）+cos²（150°-x）的值
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sin(210°+x) + [cos(150°-x)]^2
=sin[180°+(30°+x)] + {cos[180°-(30°+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 - 1/16
=11/16
=sin[180°+(30°+x)] + {cos[180°-(30°+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 - 1/16
=11/16
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