To prove that angle AOC is equal to angle DOB, we can use the property of vertically opposite angles.
Vertical angles are formed by two intersecting lines and are always congruent (equal).
Let's assume that line OC intersects line OD at point P.
Now, we have two pairs of vertically opposite angles:
- Angle AOC and angle BOD
- Angle AOP and angle BOP
Since angle AOP and angle BOP are vertically opposite angles, they are equal.
Using the same reasoning, angle COB and angle DOP are also equal, as they are vertically opposite angles.
Therefore, we conclude that angle AOC is equal to angle BOD because they are both equal to their corresponding pairs of vertically opposite angles: angle AOP and angle BOP, and angle COB and angle DOP.
