AC and BD are the diameters of the circle centered on O. The angle ACB is 13 °. Find the corner AOD.

1. Draw a circle;

2. mark its center with point O;

3. Draw two diameters AC and BD;

4. We connect points A and D, B and C, we get two identical isosceles triangles:

ΔAOD = ΔВOC,

5. AC = OC = BO = OD = R;

6. <ACB = <CAD = 13 °;

<CAD = <ADB = <OAD = <ADO = 13 °;

7. <AOD = 180 ° – <OAD – <ADO = 180 ° – 13 ° – 13 ° = 154 °.

Answer: 154 °.