a) $\displaystyle b = cosx $Given that $\displaystyle a = 4 sec x , b = cosx , c = cotx $

a) express b in terms of a

b) show that $\displaystyle c^{2} = \frac{16}{a^{2} - 16} $

$\displaystyle a = \frac{4}{cosx} $

$\displaystyle a = \frac{4}{b} $

$\displaystyle b = \frac{4}{a} $

having trouble with part 'b';