设x,y属于R,向量a=(x+根号3,y)b=(x-根号3,y)且|a|+|b|=41.求点M(x,y)的轨迹C的方程.2.过点P(0,2)作直线l交曲线C于A,B两点,又O为坐标原点,若OA·OB=12/5,求直线l的倾斜角.第一定义怎么
1.△ABC中,设BC=a,CA=b,则AB=多少?A.a+bB.-a-bC.a-bD.b-a2.化简:AB+BC+CDA.CBB.DAC.ADD.BC3.在△ABC中,a,b,c,分别为角A,B,C的对边,且4sin^2[(B+C)/2]-cos2A=7/2.(1)求∠A的大小;(2)若a=√3,b+a=3,求a和c的值.4.设锐角三角
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