(lntan0.5x)'
=(1/tan0.5x)*(tan0.5x)'
=(cos0.5x/sin0.5x)*sec²0.5x*(0.5x)'
=(cos0.5x/sin0.5x)*(1/cos²0.5x)*0.5
=1/(2sin0.5xcox0.5x)
=1/sinx
=cscx