Sabemos que a secante é o inverso do coseno, isto é:
[tex]secx = \frac{1}{cosx}[/tex]
Ou seja:
[tex]\text{Se} \ cos x = \frac{2}{7}, sec = \frac{7}{2} \\\\ \text{Temos que:} \\\\ sec x = \frac{7}{2} \\\\ sec x = \frac{m}{4} \\\\ \frac{7}{2} = \frac{m}{4} \\\\ 2m = 28 \\\\ \boxed{m = 14}[/tex]
