<s>
Zhao	O
Youqin	O
started	O
with	O
an	O
inscribed	O
square	O
in	O
a	O
circle	O
with	O
radius	B-Protocol
r	O
.	O
</s>
<s>
Extend	O
the	O
perpendicular	O
line	O
d	O
to	O
dissect	O
the	O
circle	O
into	O
an	O
octagon	B-Application
;	O
denotes	O
the	O
length	O
of	O
one	O
side	O
of	O
octagon	B-Application
.	O
</s>
