∴∠ABC=90，

∵OD⊥AC，

∴∠ Addo = 90 degrees,

∴△ABC∽△ADO，

∴ODBC

=AO

Alternating current

That is, OD=AO×BC.

Alternating current

In △ABC,

∠BAC=30，

∴AC=2BC=8 3

AB= AC 2

In 2 BC

= 12,

∴OA=6=BO，

∴OD=AO×BC

Alternating current

=6×4 3

8 3

=3.