1) In a circle, O is the centre of the circle. There are two adjacent chords AB and BC, which connect to form a triangle ABC. Another triangle is also formed off chord AB when it connects to O, forming triangle AOB. If angle OAB = angle BCA, find angle AOB.
2) In a circle, AC and DB are two chords, which intersect at X. AX = CX, so prove AC // DB.
3) Find the 5 unknown angles in these 4 circles.
Thanks for any help.