Barron's SAT Math II. Page 12 #2

A function is said to be even if f(x)=-f(x). Which of the following is NOT an even function

a) y= lxl

b)y=secx

c) y=logx^2

d) y=x^2+sinx

e) y=3x^4-2x^2+17

I know a), c) and e) are even functions. But I can't decide between b) and d). What does sec in y=secx mean exactly?

Thanks in advance! (: