可设向量c=(x,y).则向量a-c=(1,0)-(x,y)=(1-x,-y),b-c=(1,1)-(x,y)=(1-x,1-y).由题设可得(1-x,-y)·(1-x,1-y)=0.===>(1-x)²-y(1-y)=0.===>(x-1)²+[y-(1/2)]²=1/4.换元,可设x=1+(cost)/2.y=(1+sint)/2...