theorem Th80:
for
p being
Point of
(TOP-REAL 2) st
p `2 = 0 holds
for
x being
Real for
a being non
negative Real for
y,
r being
positive Real st
(+ (x,y,r)) . p > a holds
(
|.(|[x,y]| - p).| > r * a & ex
r1 being
positive Real st
(
r1 = (|.(|[x,y]| - p).| - (r * a)) / 2 &
(Ball (|[(p `1),r1]|,r1)) \/ {p} c= (+ (x,y,r)) " ].a,1.] ) )