Question Number 152617 by eman_64 last updated on 30/Aug/21
Commented by mr W last updated on 30/Aug/21
$${L}=\underset{{x}\rightarrow\frac{\pi}{\mathrm{6}}} {\mathrm{lim}}\frac{−\mathrm{cos}\:\left(\frac{\pi}{\mathrm{6}}−{x}\right)}{−\mathrm{4cos}\:{x}}=\frac{\mathrm{1}}{\mathrm{4}×\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}}=\frac{\mathrm{1}}{\mathrm{2}\sqrt{\mathrm{3}}} \\ $$