Compute the derivative of the function $()=$cot$(21)$f$($x$)=$cot$(2$x$1)?$

Select one:

a$.$

$2$sin$(21)2$sin$(2$x$1)$

b$.$

$2$csc$2(21)2$csc$2(2$x$1)$

c$.$

$2$csc$2(21)2$csc$2(2$x$1)$

d$.$

$$csc$2(21)$