Question

取园x^2+y^2=R^2上任意一点A,园x^2+y^2=r^2任意一点B(R>r),以B点作AB的垂直线,交园x^2+

Answer 1

a(x1,y1),b(x2,y2),c(x3,y3),d(x4,y4)

(x1-x3)^2+(y1-y3)^2=(x2-x4)^2+(y2-y4)^2

R^2-2x1*x3+R^2-2*y1*y3=r^2-2*x2*x4-2*y2*y4+x4^2+y4^2 (1)

x1+x3=x2+x4,y1+y3=y2+y4,x3^2+y3^2=R^2,x1^2+y1^2=r^2

(1)=4R^2-(x2+x4)^2-(y2+y4)^2=r^2-x2x4-y2y4+x4^2+y4^2

x4^2+y4^2=2R^2-r^2

写了这么多加点分吧,累死我了