In a couple of trig identities, esp to do with integrals and derivatives, you see a relationship between tan(x) and sec(x). Similarly between csc(x) and cot(x).
$ \frac{d}{dx}\tan(x) = \sec^2(x) $
$ \frac{d}{dx}\sec(x) = \sec(x) \tan(x) $
$ tan^2(x) + 1 = sec^2(x) $
Is there a name for this apparent relationship between $\tan(x)$ and $\sec(x)$? Something like "complimentary", or "counterparts" of one another..?