4) secx/1 +cot²x
[tex] \frac{sec \: x}{1 + cot { \: x}^{2} } = \frac{sec \: x}{cosec \: {x}^{2} } = \frac{ \frac{1}{cos \: x} }{ \frac{1}{sin \: x} } = \frac{sin \: x}{cos \: x} = tan \: x[/tex]
