Differentiate $y=cot(\frac{x}{2})$

Select one:

$a.-2cot(\frac{x}{4})cs{c}^2(\frac{x}{4})$

$b.-\frac{1}{2}cs{c}^2(\frac{x}{2})$

$C.-\frac{1}{2}cot(\frac{x}{4})cs{c}^2(\frac{x}{2})$

$d.-cs{c}^2(\frac{x}{2})$