We know that,
#color(red)((1)1-cos^2theta=sin^2theta#
#color(blue)((2)cscx=1/sinx#
#color(violet)((3)cotx=cosx/sinx#
Here,
#(sinx/(1-cosx))-cscx =(sinx/(1-cosx)xx(1+cosx)/(1+cosx))-cscx#
#color(white)((sinx/(1-cosx))-cscx) =(sinx(1+cosx))/color(red)((1-cos^2x))-cscx#
#color(white)((sinx/(1-cosx))-cscx )=(sinx(1+cosx))/color(red)(sin^2x)-cscxtoApplycolor(red)((1)#
#color(white)((sinx/(1-cosx))-cscx )=(1+cosx)/sinx-cscx#
#color(white)((sinx/(1-cosx))-cscx) =cancel(1/sinx)+cosx/sinx-cancel(1/sinx)toApplycolor(blue)((2)#
#color(white)((sinx/(1-cosx))-cscx) =cosx/sinx...toApplycolor(violet)((3)#
#(sinx/(1-cosx))-cscx =cotx#