A circle is centered at $O$, $\overline{AB}$ is a diameter and $C$ is a point on the circle with $\angle COB = 50^\circ$.  What is the degree measure of $\angle CAB$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
A circle is centered at $O$, $\overline{AB}$ is a diameter and $C$ is a point on the circle with $\angle COB = 50^\circ$.  What is the degree measure of $\angle CAB$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
25^\circ
A circle is centered at $O$, $\overline{AB}$ is a diameter and $C$ is a point on the circle with $\angle COB = 50^\circ$.  What is the degree measure of $\angle CAB$?
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