Answer:
[tex]\boxed{<a = 62 degrees}[/tex]
[tex]\boxed{<b = 118 degrees}[/tex]
Step-by-step explanation:
A) If AB is a diameter, Then ACB is a 90 degrees angle because In a semi-circle (AB is a diameter which divides the circle into 2 equal parts), the angle opposite to the diameter is of 90 degrees.
So, <ACB = 90 degrees
Then <a = 180-90-28
=> <a = 62 degrees
B) The opposite interior angles of a quadrilateral inscribed in a circle add up to 180 degrees.
So,
=> <a + <b = 180
=> <b = 180-62
=> <b = 118 degrees
