k 5. Use the fact that e" = = 1+x+ + + ... for all x. K! 2! 3! k=0 (a) The antiderivatives of e- /2 are not elementary functions; this means that, no matter how hard you try, you will not be able to evaluate / e-/2 dx as a finite sum of functions we know. Instead, find a power series representation of the indefinite integral / e-/2 dx. For what x is your representation valid? (b) Find a series whose sum is e -x /2 dx