C complex number and printf

printf("%f + i%f\n", creal(result), cimag(result));

I don't believe there's a specific format specifier for the C99 complex type.

Let %+f choose the correct sign for you for imaginary part:

printf("%f%+fi\n", crealf(I), cimagf(I));

Output:

0.000000+1.000000i

Note that i is at the end.