Question 1003488
From
(sinx/1-cosx)=(1+cosx/sinx)
we multiply the left side by (1+cosx)/(1+cosx) and get

sinx(1+cosx)/(1-cos^2x)=(1+cosx/sinx)
sinx(1+cosx)/sin^2x = (1+cosx/sinx)
(1+cosx/sinx) = (1+cosx/sinx)