Prove that: $\dfrac{1 - sin2A}{cos2A} = sec2A - tan2A$.

Solution:

Taking LHS

$= \dfrac{1 - sin2A}{cos2A}$

Separately write the terms now

$= \dfrac{1}{cos2A} - \dfrac{sin2A}{cos2A}$

Use the trigonometric identities now

$= sec2A - tan2A$

= RHS

#proved