First of all, in the definition domain, you should pay attention to the denominator, radical sign, absolute value, square, cube and so on. Positive and negative and not equal to 0. In the value domain, see the complete function, and remove the parts that are not in the definition domain, such as two small problems. Denominator is not 0, cosx≠ 1, and domain is x≠2kπ, 0.

Second, change it to y=Acos[w(x+b)], the amplitude is a, the period is 2π/w, and the zero point is w(x+b)=kπ+π/2, that is, x=kπ/w+π/2w-b, and the topic is y = 1/2cos.