p=cos a/cos 2a怎么化简?

∵p=√(x^2+y^2)p*cosa=xp*sina=y∴ 由p=cos a/cos 2a两边取倒数,得1/p=cos2a/cosa=[(cosa)^2-(sina)^2]/cosa=cosa-(sina)^2/cosa1=p*cosa-p*sina*p*sina/(p*cosa)即x-y^2/x=1x^2-y^2=xx^2-x-y^2=0(x-1/2)^2-y^2=1/4...