If angle $x$ lies in the third quadrant and $\cos x = -\frac{20}{29},$ find $\tan x.$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If angle $x$ lies in the third quadrant and $\cos x = -\frac{20}{29},$ find $\tan x.$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\frac{21}{20}
If angle $x$ lies in the third quadrant and $\cos x = -\frac{20}{29},$ find $\tan x.$
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