Question 1068288
.
<pre>
0.  Make a sketch to follow my arguments.


1.  Consider the angle CAB.

    This angle is right angle, since it leans the diameter.


2.  Consider the angle DAB.

    This angle is right angle, since it leans the diameter.


3.  Since both angles CAB and DAB are right angles, the rays AC and AD make one straight line.
</pre>

Proved and solved.