1. The problem statement, all variables and given/known data sqrt(R)*(cos a + i sin a) = (n - ik - 1) / (n - ik + 1) what is n in terms of others. "i" is imaginary part. By using this equation, can you seperate imaginary and real part for finding R= (1-R) / [1+R-2*sqrt(R) * cos a] and K = 2 * sqrt(R) * sin a / [1 + R - 2 * sqrt (R) * cos a ] thank you. 2. Relevant equations 3. The attempt at a solution i have found n iK + [ (1+sqr(R) * (Cosa+isina) ]/[(1-sqr(R) * (Cosa+isina)] but i couldn't separete imaginary and real parts. if i separeta n has not imaginary part. by using this info. we can gain K.