The function whose domain excludes zero is in which ax^n, where a and n are any numbers, occupies the denominator of a fraction, because division by zero is undefinable. Similarly, a function containing log(x), where log is to any base, excludes 0 in its domain. Because sin(x) and tan(x) are both zero when x=0, a function containing cosec(x) and/or cot(x) excludes zero in its domain. The denominator of a fraction containing only terms involving x (i.e., ax^n, sin(x), tan(x)) renders the fraction undefinable when x=0. A function containing such terms excludes zero in its domain.
