Given f(x) = x² - sec(x) , find f'(x) .
a) f'(x) = 2x + sec(x) tan(x)
b) f'(x) = 2x - sec(x) tan(x)
c) f'(x) = 2x + sec²(x)
d) f'(x) = 2x - sec²(x)