The graph of y = cos(Θ) is a curve that oscillates between -1 and 1, with a period of 2π.
To see why, let's consider the unit circle, which is a circle with a radius of 1 centered at the origin of the Cartesian plane. Suppose we start at the point (1, 0) on the unit circle and move counterclockwise along the circle. As we move, we trace out an angle Θ, which is measured in radians.
The x-coordinate of the point we reach after moving through an angle Θ is given by cos(Θ), and the y-coordinate is given by sin(Θ). So if we plot the x-coordinate as a function of Θ, we get the graph of y = cos(Θ).
As we move counterclockwise around the unit circle, the x-coordinate of the point we reach oscillates between -1 and 1, as shown in the following graph:
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This graph repeats itself every 2π radians, which is the period of the function.