We propose a general formalism to describe accurately the angular dependence of the magnetoresistance. A parabolic band model is used to determine without approximation the conductance of arbitrary complex heterostructures. Simple analytical expressions are obtained in some limit cases. Particularly, we show that significant deviation from the cosine dependence is expected for ferromagnetic barriers. Numerical computations are used to quantify the deviation from the cosine dependence for normal and ferromagnetic barriers and support the precedent conclusion. Finally, the influence of the applied voltage on the angular dependence of magnetoresistance is discussed.