mejack1324

x^2 + y^2 =c^2 (a)
x=c-y   (b)

(b)代入去(a)

(C-Y)^2 +Y^2= C^2
C^2-2CY+Y^2+Y^2=C^2
2Y^2=2CY
Y^2=CY
y^2-cy=0
y(y-c)=0
y=0 or y-c=0
y=0 or y=c

if y=0
x+0=c
x=c

if y=c
x+c=c
x=0

所有.x=0 , y =0 ,y=c ,x=c