Decide whether to integrate with respect to x or y. Then find the area of the region

$\displaystyle y = 7 \cos x, y = (6 sec(x))^2, x = -\pi / 4, x = \pi / 4 $

i used the formula: $\displaystyle A = \int_a^b(f(x)-g(x)) dx $

$\displaystyle A = \int_a^b ((6 sec(x))^2 - 7 cosx)dx$

$\displaystyle a = -\pi / 4 , b = -\pi / 4 $

not sure what to do next