NOT TO SCALE $$\(A, B\)$$ and $$\(C\)$$ are three points on a circle, centre $$\(O\)$$. $$\(D E\)$$ is a tangent to the circle at $$\(A\)$$. Angle $$\(A C O=35^{\circ}\)$$ and angle $$\(B C O=40^{\circ}\)$$. Find angle $$\(O A B\)$$. Angle $$\(O A B=\)$$ ............................................

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