interpolate()

To provide the ability to interpolate between the values produced by rk4p480(), write a function of the following form in ``p480.c'':

void interpolate(double f[],int N)

Output:

• f[k]: values of f[] on all points

Input:

• f[k]: values of f[] on even points only
• N: total number of points

Your function should interpolate the odd values of f[] from the even values according to the formula

For the special endpoint cases, k=1 and k=N-1, you may take and , respectively.