+188 AC is tangent to circle O at A. If m arc BY = 24, what is m∠YAC? (The figure is not drawn to scale.) 
A. 132
B. 48
C. 78
D. 156
+129849 If BY = 24, then m<BAY = 12 [ an inscribed angle measures 1/2 of its intercepted arc ]
And m<BAC = 90
And m<BAC = m<BAY + m< YAC
So
90 = 12 + m<YAC subtract 12 from both sides
78 = m<YAC
"C" is correct
