In the last four decades, the orthogonal functions approach has been extensively applied to study problems like analysis, identification, and control of continuous-time dynamical systems. The success of this approach lies in the fact that it converts calculus into algebra approximately in the sense of least squares. Sine-cosine functions are a class of orthogonal functions, and they were applied to study the optimal control problem with some success. In order to have a computationally attractive method for solving the optimal control problem via sine-cosine functions, an attempt was made. In this note, we show that the Fourier series approach to the optimal control problem in a previous paper is incorrect.