I need help deriving the expression for:

(a) sinhz/z^2 = 1/z + summation from n=0 to infinity z^2n+1/(2n+3)!

0<|z|<infinity

(b)z^3cosh(1/z) = z/2 + z^3 + summation from n=1 to infinity (1/(2n+2)!)*(1/z^2n-1) 0<|z|<infinity

Im lost if anyone can help please!!!