Use L'Hospital to determine the following limit (where t\displaystyle {t} is regarded as a constant):

limω13cos(ωt)cos(13t)169ω2\displaystyle \lim_{{\omega\to{13}}}\frac{{{\cos{{\left(\omega{t}\right)}}}-{\cos{{\left({13}{t}\right)}}}}}{{{169}-\omega^{{2}}}}