Question:
Find the value of the trigonometric function $\cot \left(-\frac{15 \pi}{4}\right)$
Solution:
It is known that the values of $\cot x$ repeat after an interval of $\pi$ or $180^{\circ}$.
$\therefore \cot \left(-\frac{15 \pi}{4}\right)=\cot \left(-\frac{15 \pi}{4}+4 \pi\right)=\cot \frac{\pi}{4}=1$