Use the (x,y) coordinates in the figure to find the value of the trigonometric function at the indicated real number, t, or state that the expression is undefined.
cos 0
Looking at the figure or graph, we can see that at the point representing t = 0, the x-coordinate is 1 and the y-coordinate is 0.
Since the x-coordinate represents the value of the cosine function, we can conclude that cos 0 = 1.