倾斜角为4/π?
是不是π/4?
如果是则
k=tanπ/4=1
y=x+b
x^2/4+x^2+2bx+b^2=1
5x^2+8bx+4b^2-4=0
x1+x2=-8b/5
方程有解
64b^2-80b^2+80>=0
b^2<=5
-√5<=b<=√5
y1+y2=(x1+b)+(x2+b)=(x1+x2)+2b=2b/5
AB中点x=(x1+x2)/2=-4b/5
-√5<=b<=√5
-4√5/5<=-4b/5=x<=4√5/5
y=(y1+y2)/2=b/5
x=-4y
y=-x/4,其中-4√5/5<=x<=4√5/5