cos^2(x) refers to squaring (multiplying by itself) the cosine function with angle x. This results in values ranging from 0 to 1 inclusively since cosine oscillates between -1 and 1.
Related terms
Trigonometric Function: A function that relates angles to ratios of side lengths in triangles.
Composite Function: A function that combines two or more functions, where the output of one function becomes the input for another.
Domain: The set of all possible input values for a given function.