Polar and coordinase complex numbers are two different ways of represent the same complex numbers. The polar way uses the following formula: Me^(anglej), where M is the modulus of the complex number and can be obtained by Pithagoras´Theorem from the vector coordinates of the number. On the other hand, the angle of the number is calculated by the arctan(vertical coordinate/horizontal coordinate). The cartesian way uses also the modulus and that angle, by in a different way. It is determined by applying Mcos(angle)+jM*sin(angle) And then I would show to the student a numerical example and we would analysed together some different exceptions.