(Geometry) Circle, angles and tangents problem Let P be an external point of a circle with center in O and also the intersection of two lines r and s that are tangent to the circle. If PAB is a triangle such that AB is also also tangent to the circle, find AÔB knowing that P = 40°.
I draw the problem:

Then I tried to solve it, found some relations, but don't know how to proceed.

I highly suspect that PAB is isosceles, but couldn't prove it.

Two tangents meet at a point. Therefore MP = NP. Only if OTP is a straight line, triangles MPN and APB are similar, hence both isoceles in this particular case - otherwise the triangles are not similar and only MPN is isoceles.
