$\operatorname{arcsec} (2^x)$.More importantly, for a composite function involving three functions (say, f , g and h ), applying the Chain Rule twice yields that:\begin{align*} f(g[h(c)])’ & = f'(g[h(c)]) \, \left[ g[h(c)] \right]’ \\ & = f'(g[h(c)]) \...