13
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
In a triangle, two of the side lengths are 7 and 8, and the angle between them is $120^\circ.$  Find the length of the third side.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
13
In a triangle, two of the side lengths are 7 and 8, and the angle between them is $120^\circ.$  Find the length of the third side.
train