(1 - sin(x)^2) / (sin(x) - csc(x))
= cos(x)^2 / (sin(x) - csc(x))
= cos(x)^2 / ((sin(x)^2 / sin(x)) - csc(x))
= cos(x)^2 / ((sin(x)^2 / sin(x)) - (1 / sin(x)))
= cos(x)^2 / ((sin(x)^2 - 1) / sin(x))
= cos(x)^2 / (-(1 - sin(x)^2) / sin(x))
= cos(x)^2 / (-cos(x)^2 / sin(x))
= cos(x)^2 * (sin(x) / -cos(x)^2)
= cos(x)^2 * (-sin(x) / cos(x)^2)
= -sin(x)