向量OZ1=(3,2sinA),向量OZ2=(sinA,1+cosA)∵OZ1//OZ2,∴3(1+cosA)=2sinA*sinA,即3(1+cosA)=2(1-(cosA)^2)即2(cosA)^2+3cosA+1=0即cosA=-1/2或cosA=-1(角A为三角形内角,舍去),∴cosA=-1/2即角A=120°a^2=b^2+c^2-2bccosA=b^2+c^2+bc,又a^2=(√7)^2(c-b)^2=7(b-c)^2=7b^2-14bc+7c^2,∴b^2+c^2+bc=7b^2-14bc+7c^2即2b^2-5bc+2c^2=0,即2(b/c)^2-5b/c+2=0即b/c=2或1/2即b=2c或c=
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