Take point d of OA and connect CD.

D is the midpoint of OA, so OD=AD.

So CD is perpendicular to OA (vertical diameter theorem)

Because c and d are the midpoint of ob and OA, respectively.

So CD//AB

It is proved that the triangle OCD is similar to the triangle OBA.

So the angle = Bowie angle = 90.

So OA is perpendicular to AB.

So AB is the tangent of circle O.

Finally finished the process, but it's a little simple ~ ~ I hope I can help you ~ ~

Ask me if you don't understand the process.

Is there a problem with this question ~ ~ ~ is there a condition? After thinking for a long time, I still can't prove it ~ ~ ~ depressed ~ ~

The opposite side of angle B is half of the hypotenuse. Then let the triangle ABO be a right triangle. It seems that the conditions are not enough ~ ~ ~

PS: If the meaning of the question is not less, the picture is correct ~ ~ This question will not be done ~ ~ I have seen it many times ~ ~ ~