Find the measure of BAC The figure is not drawn to scale Sol

Find the measure of BAC. (The figure is not drawn to scale.)

We know OA=OB= radius of the circle,
therefore, m(OAB) = m(OBA) = x
Given m(BOC) = 57,
m(AOB) + M(BOC) = 180
m(AOB) = 180 - 57
m(AOB) = 123
In Triangle AOB,
m(AOB) + m(OBA) + m(OAB) = 180
123 + x + x = 180
2x = 57
x = 57/2 = 28.5
m(BAC) = 28.5