I having some problem proving a identity.

Prove:

$\displaystyle

(sec^2x )/tanx = (cot^2x - tan^2x) / (cotx - tanx)

$

i start by the left side so i get (1+tan^2x) / tan

, and i then i convert tans to sins and cons, so i get (1+(sinX^2/con^2x))/(sinx/sin)

after that i am lost, i dont know if i should start by the left side.

plz help