Draw AO, BO, AB and BP.......label the intersection of TO and AB as point F
With the above additions, I believe the image below is what you describe :

By SSS, triangle ATO congruent to triangle BTO.....thus angle ATO = angle BTO
Thus, by SAS, triangle ATF congruent to triangle BTF
Thus, FA = FB
And a radius bisecting a chord does so at right angles... so, OP is perpendicular to AB
Thus, by LL, triangle PAF congruent to triangle PBF
Thus angle PAF = angle PBF
And, by Euclid, m< TAP = 1/2 minor arc PA
But, angle PBF = angle PBA .....and PBA is an inscribed angle = 1/2 minor arc PA
But, it was shown that angle PBF = angle PAF......thus, angle PAF also = 1/2 minor arc PA
So.......m<TAP = m<PAF = m<PAB
So....m<TAP = m<PAB, and AP bisects TAB
