$\displaystyle \sin\theta\sec\theta\cot\theta \equiv 1$

$\displaystyle \d{L}\d{H}\d{S} = \sin\theta\sec\theta\cot\theta$

$\displaystyle = \sin\theta \times \frac{1}{\cos\theta} \times \frac{\cos\theta}{\sin\theta}$

After this step I donno what to do. I should proved that $\displaystyle sin\theta\sec\theta\cot\theta$ is equal to $\displaystyle 1$, can anyone please help me!

Thnx in advance!