consider
x1
being
Point
of
R
,
x2
being
Point
of
S
such that
A1
:
x
=
[
x1
,
x2
]
by
BORSUK_1:10
;
f
.
[
x1
,
x2
]
is
Point
of
T
;
hence
f
.
x
is
Point
of
T
by
A1
;
:: thesis:
verum