Ineed to simplify sec^2(x)/sec^2(x)-1

How to do this , and can some one explain

This is about circle theorems. someone asap : (

The statements below can be used to prove that the triangles are similar. ? △abc ~ △xyz by the sss similarity theorem. which mathematical statement is missing? ∠b ≅ ∠y ∠b ≅ ∠z