2025 IGCSE 0580 May/June P21 Q10

\(A\), \(B\) and \(C\) are three points on a circle, centre \(O\).

\(DE\) is a tangent to the circle at \(A\).

Angle \(ACO=35^\circ\) and angle \(BCO=40^\circ\).

Find

1. angle \(AOC\)[1]
2. angle \(ABC\)[1]
3. angle \(DAC\)[1]
4. angle \(OAB\).[1]