Connect OP and meet AB at m.

∫PA and PB are tangents of circle O.

∴PA

=PB

and

PO average score ∠APB

∴PO⊥AB

∴AM

=

Bachelor of medicine

∵AO

=

man

∴OM

=

1/2

B.C.

=

1/2

∵∠PAO

=

Ampere

=

90

∠OPA is the angle of * * *

∴△PAO∽△PMA

∴PA？

=

PM*PO

Namely: 3

=

(PO

-

1/2)* Purchase order

∴PO

=

2

∴AO

=

√(PO？

-

AP？ )

=

1

So the radius of the circle is 1.