[질문] 세점(━3━2)(━21)(1 0)을지나는원의둘레의길이는?

좌표(X1,X2,X3,Y1,Y2,Y3)이고(Xc Yc)(X1-Xc)^2 + (Y1-Yc)^2 = r^2 (X2-Xc)^2 + (Y2-Yc)^2 = r^2 (X3-Xc)^2 + (Y3-Yc)^2 = r^2 배운 Ax^2 + By^2 + Cxy + D