find the radius of this circle

A, B, C, D are points on a circle of centre O and TA is the tangent to the circle at A.

TA = 7.1 cm

AD = 4.5 cm

Basically if we were to draw this circle we would first draw (Clockwise) the point D on the circle then A then C and then B.

Point T being outside of the circle slightly on the right of it.

Now angle BDA = 36 degrees and DAT = 28 degrees

**From this info I need to find the radius of the circle and say if OT bisects AD?**

I have demonstrated (using the circle property) that angle BOA = 72 degrees and BCA = 144 degrees and also OAD = 62 degrees.

But how can I find the radius and prove the bisection? Please any hints or answers to this treaky one :-)