find the maclaurin series for f(x) = coshx

the answer is = 1 + x^2 / 2! + x^4 / 4! + x^6 / 6! + ...

my question: How is the 6th derivative positive? i believe its a -coshx?

also, whats the difference between coshx and just cosx?

this particular problem was unique to me. thanks