how would you create an equation for sec(2x) using only sec(x) and csc(x)?

Use the relation sec(2x) = 1/cos(2x) and the formula for cos(2x) in terms of sin x and/or cos x.

sec(2x) = 1/cos(2x) = 1/[1 - 2 sin^2x]
= 1/[1 - 2/csc^2x]