Trigonometry Issue

In the Trigonometry module, I found that sine and cosine are not described as functions different only by a phase shift. In the "writing equations for sinusoidal functions," the video lesson distinguishes between a sinusoidal graph being sine or cosine; but the graph could really be described by either function, as long as the appropriate shifts are accounted for. And in the quizzes, only one trigonometric function (either a sine or a cosine function) is accepted, when again either could be used to accurately describe the graph.