Which shows the graph of a cosine curve with amplitude 3, period pi/4 and a< 0?

Given that you don't provide a graph, I will try to solve this problem using the data written in the question. A cosine function is given by the formula:



According to the statement, the amplitude of this function is equal to . So we need to find the period that is related to like this:



 Accordingly:



So this graph is shown in the figure below. The frequency of this function is 8 times the frequency of the function and the amplitude acts as a scaling factor.