\(\frac{1-sinθ}{1+sinθ}\) = \(\frac{1-sinθ}{1+sinθ}\times\frac{1-sinθ}{1-sinθ}\)
= \(\frac{(1-sinθ)^2}{1-sin^2θ}\)
= \(\frac{(1-sinθ)^2}{cos^2θ}\)
= \(\Big(\frac{1-sinθ}{cosθ}\Big)^2\)
= \(\Big(\frac{1}{cosθ}-\frac{sinθ}{cosθ}\Big)^2\)
= (secθ - tanθ)2
Hence Proved.