[tex]cos(\theta)=\cfrac{\stackrel{adjacent}{12}}{\underset{hypotenuse}{13}}\implies cos^{-1}[cos(\theta)]=cos^{-1}\left( \cfrac{12}{13} \right) \\\\\\ \theta =cos^{-1}\left( \cfrac{12}{13} \right)\implies \theta \approx 22.62^o[/tex]
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