The funtion f is defined by the power series

f(x)= the sum n=0 to infiniti ((-1)^nx^(2n))/(2n+1)!

Find f'(0) and f''(0) determine whether f has a local maximum, a local minimum, or neither at x=0

Show that 1-(1/3!0 approximates f(1) with error less than 1/100

Show that y=f(x) is a solution to the differential equation xy' + y = cosx

any help is greatly apprectiated