#f(x) = csc(3x^2-x)#
#f'(x) = -csc(3x^2-x)cot(3x^2-x) * d/dx(3x^2-x)# (cscx derivative and chain rule )
#f'(x) = -csc(3x^2-x)cot(3x^2-x) * (6x-1)#
derivative of #csc(x)#:
#csc(x) = 1/sin(x)#
#d/dx(csc(x)) = d/dx(1/sin(x))#
#=(sin(x)d/dx(1)-1(d/dx(sin(x))))/(sin^2(x))#
#=(sin(x)(0)-(cos(x)))/(sin^2(x))#
#=(-(cos(x)))/(sin^2(x))#
#=-1/sin(x) * cos(x)/sin(x)#
#=-csc(x)cot(x)#