已知向量a=[cos(3x/2),sin(3x/2

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|向量a+向量b|=|cos(3x/2)+cos(x/2),sin(3x/2)-sin(x/2)|=[cos(3x/2)+cos(x/2)]^2+[sin(3x/2)-sin(x/2)]^2=[cos(3x/2)]^2+[cos(x/2)]^2+[sin(3x/2)]^2+[sin(x/2)]^2=2 cos(3x/2)cos(x/2)-sin(3x/2)sin(x/2)-4*2=cos(2x)-8=-9

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